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  • 51.
    Hansdotter, Frida I.
    et al.
    Public Health Agency Sweden, Sweden.
    Magnusson, Måns
    Linköping University, Department of Computer and Information Science, Statistics. Linköping University, Faculty of Science & Engineering.
    Kuhlmann-Berenzon, Sharon
    Public Health Agency Sweden, Sweden.
    Hulth, Anette
    Public Health Agency Sweden, Sweden.
    Sundstrom, Kristian
    Lund University, Sweden.
    Hedlund, Kjell-Olof
    Swedish Institute Communicable Disease Control, Linkoping, Sweden.
    Andersson, Yvonne
    Swedish Institute Communicable Disease Control, Linkoping, Sweden.
    The incidence of acute gastrointestinal illness in Sweden2015In: Scandinavian Journal of Public Health, ISSN 1403-4948, E-ISSN 1651-1905, Vol. 43, no 5, p. 540-547Article in journal (Refereed)
    Abstract [en]

    Aims: The aim of this study was to estimate the self-reported domestic incidence of acute gastrointestinal illness in the Swedish population irrespective of route of transmission or type of pathogen causing the disease. Previous studies in Sweden have primarily focused on incidence of acute gastrointestinal illness related to consumption of contaminated food and drinking water. Methods: In May 2009, we sent a questionnaire to 4000 randomly selected persons aged 0-85 years, asking about the number of episodes of stomach disease during the last 12 months. To validate the data on symptoms, we compared the study results with anonymous queries submitted to a Swedish medical website. Results: The response rate was 64%. We estimated that a total number of 2744,778 acute gastrointestinal illness episodes (95% confidence intervals 2475,641-3013,915) occurred between 1 May 2008 and 30 April 2009. Comparing the number of reported episodes with web queries indicated that the low number of episodes during the first 6 months was an effect of seasonality rather than recall bias. Further, the result of the recall bias analysis suggested that the survey captured approximately 65% of the true number of episodes among the respondents. Conclusions: The estimated number of Swedish acute gastrointestinal illness cases in this study is about five times higher than previous estimates. This study provides valuable information on the incidence of gastrointestinal symptoms in Sweden, irrespective of route of transmission, indicating a high burden of acute gastrointestinal illness, especially among children, and large societal costs, primarily due to production losses.

  • 52.
    Hedman, Johannes
    et al.
    Lunds Universitet/Lunds Tekniska Högskola.
    Ansell, Ricky
    Linköping University, Department of Physics, Chemistry and Biology, Molecular genetics. Linköping University, The Institute of Technology.
    Nordgaard, Anders
    Linköping University, Department of Computer and Information Science, Statistics. Linköping University, Faculty of Arts and Sciences.
    A ranking index for quality assessment of forensic DNA profiles2010In: BMC Research Notes, ISSN 1756-0500, Vol. 3, no 290Article in journal (Refereed)
    Abstract [en]

    Background

    Assessment of DNA profile quality is vital in forensic DNA analysis, both in order to determine the evidentiary value of DNA results and to compare the performance of different DNA analysis protocols. Generally the quality assessment is performed through manual examination of the DNA profiles based on empirical knowledge, or by comparing the intensities (allelic peak heights) of the capillary electrophoresis electropherograms.

    Results

    We recently developed a ranking index for unbiased and quantitative quality assessment of forensic DNA profiles, the forensic DNA profile index (FI) (Hedman et al. Improved forensic DNA analysis through the use of alternative DNA polymerases and statistical modeling of DNA profiles, Biotechniques 47 (2009) 951-958). FI uses electropherogram data to combine the intensities of the allelic peaks with the balances within and between loci, using Principal Components Analysis. Here we present the construction of FI. We explain the mathematical and statistical methodologies used and present details about the applied data reduction method. Thereby we show how to adapt the ranking index for any Short Tandem Repeat-based forensic DNA typing system through validation against a manual grading scale and calibration against a specific set of DNA profiles.

    Conclusions

    The developed tool provides unbiased quality assessment of forensic DNA profiles. It can be applied for any DNA profiling system based on Short Tandem Repeat markers. Apart from crime related DNA analysis, FI can therefore be used as a quality tool in paternal or familial testing as well as in disaster victim identification.

  • 53.
    Hedman, Johannes
    et al.
    Lund University.
    Nordgaard, Anders
    Linköping University, Department of Computer and Information Science, Statistics. Linköping University, Faculty of Arts and Sciences.
    Rasmusson, Birgitta
    Linköping University, Department of Clinical and Experimental Medicine, Medical Microbiology. Linköping University, Faculty of Health Sciences.
    Ansell, Ricky
    Linköping University, Department of Physics, Chemistry and Biology, Molecular genetics. Linköping University, Faculty of Health Sciences.
    Radstrom, Peter
    Lund University.
    Improved forensic DNA analysis through the use of alternative DNA polymerases and statistical modeling of DNA profiles2009In: BIOTECHNIQUES, ISSN 0736-6205, Vol. 47, no 5, p. 951-958Article in journal (Refereed)
    Abstract [en]

    DNA evidence, linking perpetrators to crime scenes, is central to many legal proceedings. However, DNA samples from crime scenes often contain PCR-inhibitory substances, which may generate blank or incomplete DNA profiles. Extensive DNA purification can be required to rid the sample of these inhibitors, although these procedures increase the risk of DNA loss. Most forensic laboratories use commercial DNA amplification kits (e.g., AmpFlSTR SGM Plus) with the DNA polymerase AmpliTaq Gold as the gold standard. Here, we show that alternative DNA polymerase-buffer systems can improve the quality of forensic DNA analysis and efficiently circumvent PCR inhibition in crime scene samples, without additional sample preparation. DNA profiles from 20 of 32 totally or partially inhibited crime scene saliva samples were significantly improved using Bio-X-Act Short, ExTaq Hot Start, or PicoMaxx High Fidelity instead of AmpliTaq Gold. A statistical model for unbiased quality control of forensic DNA profiles was developed to quantify the results. Our study demonstrates the importance of adjusting the chemistry of the PCR to enhance forensic DNA analysis and diagnostic PCR, providing an alternative to laborious sample preparation protocols.

  • 54.
    Hietala, Isak
    Linköping University, Department of Computer and Information Science, Statistics. Linköping University, Faculty of Science & Engineering.
    Frequent sequence mining on longitudinaldata: Segregation of Swedish employees2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis is based on longitudinal data of the Swedish population provided byStatistics Sweden and is conducted on behalf of the Institute for Analytical Sociology.The focus is on investigating the effectiveness of a frequent sequence miningmethod called constrained Sequential PAttern Discovery using Equivalence classes(cSPADE). The method is applied to data on segregation within workplaces, specificallyreasons for Swedish employees moving to more segregated workplaces. Thethesis found that no unique pattern of age, gender, education, unemployment, income,workplace size or foreignness index explain why a Swedish employee movesto a more segregated workplace. Evaluating the algorithm, it was found that thenumber of observations need to be smaller or an alteration of the algorithm needsto be done to reduce the process time for this specific data set.

  • 55.
    Hurtado Bodell, Miriam
    Linköping University, Department of Computer and Information Science, Statistics.
    Bayesian poll of polls for multi-party systems2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Abstract not available/Abstract ej tillgängligt.

  • 56.
    Hussian, Mohamed
    Linköping University, Department of Computer and Information Science, Statistics. Linköping University, Faculty of Arts and Sciences.
    Monotonic and Semiparametric Regression for the Detection of Trends in Environmental Quality Data2005Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Natural fluctuations in the state of the environment can long conceal or distort important trends in the human impact on our ecosystems. Accordingly, there is increasing interest in statistical normalisation techniques that can clarify the anthropogenic effects by removing meteorologically driven fluctuations and other natural variation in time series of environmental quality data. This thesis shows that semi- and nonparametric regression methods can provide effective tools for applying such normalisation to collected data. In particular, it is demonstrated how monotonic regression can be utilised in this context. A new numerical algorithm for this type of regression can accommodate two or more discrete or continuous explanatory variables, which enables simultaneous estimation of a monotonic temporal trend and correction for one or more covariates that have a monotonic relationship with the response variable under consideration. To illustrate the method, a case study of mercury levels in fish is presented, using body length and weight as covariates. Semiparametric regression techniques enable trend analyses in which a nonparametric representation of temporal trends is combined with parametrically modelled corrections for covariates. Here, it is described how such models can be employed to extract trends from data collected over several seasons, and this procedure is exemplified by discussing how temporal trends in the load of nutrients carried by the Elbe River can be detected while adjusting for water discharge and other factors. In addition, it is shown how semiparametric models can be used for joint normalisation of several time series of data.

  • 57.
    Hussian, Mohamed
    et al.
    Linköping University, Department of Computer and Information Science, Statistics. Linköping University, Faculty of Arts and Sciences.
    Grimvall, Anders
    Linköping University, Department of Computer and Information Science, Statistics. Linköping University, Faculty of Arts and Sciences.
    Trend analysis of mercury in fish using nonparametric regression2005Report (Other (popular science, discussion, etc.))
    Abstract [en]

    The International Council for the Exploration of the Sea (ICES) has longcompiled extensive data on contaminants in biota. We investigated how trendassessment of mercury in muscle tissue from fish (flounder and Atlantic cod)might be facilitated by using nonparametric regression to normalise observedlevels of this contaminant with respect to body length and weight. Specifically,we examined response surfaces and annual normalised means obtained byemploying purely additive models (AM), thin plate splines (TPS), andmonotonic regression (MR) to model mercury levels as functions of samplingyear and one or two covariates. Our analysis showed that TPS and MR modelscan be more satisfactory than purely additive models, because the formertechniques enable estimation of time-dependent relationships between themercury concentration and the covariates. However, the major obstacle fortrend assessment of the collected mercury data was a substantial interannualvariation that was related to factors other than body length and weight.Nevertheless, several time series of flounder data that started in the 1970s and1980s showed obvious downward trends, and these trends were particularly2strong in the Elbe estuary. When the analysis was limited to data collected after1990, an overall Mann-Kendall test for all sampling sites revealed astatistically significant downward trend for flounder, whereas it was notsignificant for cod.

  • 58.
    Hussian, Mohamed
    et al.
    Linköping University, Department of Computer and Information Science, Statistics. Linköping University, Faculty of Arts and Sciences.
    Grimvall, Anders
    Linköping University, Department of Computer and Information Science, Statistics. Linköping University, Faculty of Arts and Sciences.
    Burdakov, Oleg
    Linköping University, Department of Mathematics, Optimization . Linköping University, The Institute of Technology.
    Sysoev, Oleg
    Linköping University, Department of Computer and Information Science, Statistics. Linköping University, Faculty of Arts and Sciences.
    Monotonic regression for the detection of temporal trends in environmental quality data2005In: Match, ISSN 0340-6253, Vol. 54, no 3, p. 535-550Article in journal (Refereed)
  • 59.
    Hussian, Mohamed
    et al.
    Linköping University, Department of Computer and Information Science, Statistics. Linköping University, Faculty of Arts and Sciences.
    Grimvall, Anders
    Linköping University, Department of Mathematics, Statistics . Linköping University, The Institute of Technology.
    Petersen, Wilhelm
    GKSS Research Centre, Institute for Coastal Research, Geesthacht, Germany.
    Estimation of the human impact on nutrient loads carried by the Elbe River2004In: Environmental Monitoring and Assessment, ISSN 0167-6369, Vol. 96, no 1-3, p. 15-33Article in journal (Refereed)
    Abstract [en]

    The reunification of Germany led to dramatically reduced emissions of nitrogen (N) and phosphorus (P) to the environment. The aim of the present study was to examine how these exceptional decreases influenced the amounts of nutrients carried by the Elbe River to the North Sea. In particular, we attempted to extract anthropogenic signals from time series of riverine loads of nitrogen and phosphorus by developing a normalization technique that enabled removal of natural fluctuations caused by several weather-dependent variables. This analysis revealed several notable downward trends. The normalized loads of total-N and NO3-N exhibited an almost linear trend, even though the nitrogen surplus in agriculture dropped dramatically in 1990 and then slowly increased. Furthermore, the decrease in total-P loads was found to be considerably smaller close to the mouth of the river than further upstream. Studying the predictive ability of different normalization models showed the following: (i) nutrient loads were influenced primarily by water discharge; (ii) models taking into account water temperature, load of suspended particulate matter, and salinity were superior for some combinations of sampling sites and nutrient species; semiparametric normalization models were almost invariably better than ordinary regression models.

  • 60.
    Jansson, Nils-Henrik
    et al.
    Linköping University, Department of Computer and Information Science, Statistics. Linköping University, The Institute of Technology.
    Pavlov, Patrik
    Linköping University, Department of Computer and Information Science, Statistics. Linköping University, The Institute of Technology.
    Cryptosporidiumutbrottet i Östersunds kommun 2010: Påverkan på kommunens barn2013Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The purpose of this study is to analyze how children under the age of 15 years were affected by the 2010 Östersund Cryptosporidium outbreak. The data consists of responses to a questionnaire from 514 children concerning their health related to the outbreak. The questionnaire was developed by the Swedish Institute for Infectious Disease Control shortly after the outbreak. The analysis of risk factors and the analysis of symptoms associated with infection were performed using logistic regression models based on both a Bayesian and a frequentist approach. Using the two different approaches we thus consider the dataset from different angels and at the same time try to identify the differences between these two approaches. Another part of the paper presents estimates calibrated for nonresponse of the number of Cryptosporidium infections both totally and on a monthly basis. Additionally estimates of the prevalence of cases in various domain groups are presented. Finally, associations between the symptoms are investigated using logistic regression. With the same goal we performed variable clustering of the symptoms using the fuzzy clustering approach. The results shows that higher water intake, getting water thru the municipal water distribution system, Former loose stools and Gender could be identified as risk factors while the best-explanatory symptoms were watery diarrhea, abdominal or stomach pain, fever and tiredness/exhaustion.

  • 61.
    Javad, Raheel
    et al.
    Linköping University, Department of Computer and Information Science, Statistics. Linköping University, The Institute of Technology.
    Sadoghi, Amirhossein
    Linköping University, Department of Computer and Information Science, Statistics. Linköping University, The Institute of Technology.
    Best Practices for Customer Churn Prediction2009Conference paper (Other academic)
    Abstract [ar]

    Acquiring new customers in any business is much more expensive than trying to keep the existing one. This becomes more challenging for customer-oriented organizations because of saturation andfierce competition in this market. Thus a business analyst shifted their focus from building a largecustomer base into keeping customers ‘in house’ (Defensive Marketing). Acquiring new customers ismore expensive than retaining existing customers. Because of these reservations the need of step bystep process to make sure the appropriate selection of dataset and model to guarantee the qualityof forecasted result become more important. In this paper will use the best practices of data miningprocesses to model the whole problem. We will use standard data mining process CRISP-DM tostructure customer churn prediction model. Discuss best variable selection techniques with reasonrelative to telecom industry. We will investigate the pros & cons of LOLIMOT and ADTreesLogit modelto find out the appropriate one. The idea is to provide detailed decision analysis for the decision makersand other stakeholders to give them better insight of their business for making strategic decisions. Datacan be used from data warehouses, data marts or specialized data mining systems.

  • 62.
    Johansson, Henrik
    et al.
    Linköping University, Department of Computer and Information Science, Statistics. Linköping University.
    Kardell, Mathias
    Linköping University, Department of Computer and Information Science, Statistics. Linköping University.
    Demografisk sammansättning samt beteende hos medlemmar i panel2010Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The use of marketing research panels are a more and more frequently used source of information for studies within many different branches. The purpose of this report is to investigate the demographic composition of panels and compare it with the population of Sweden, a possible change in behaviour of respondents, and if the source of recruitment is the cause of possible differences in study results. The study was commissioned by Norstats Linkoping office. Sources for the data material include Norstat’s recruitment process and their two main panels with different recruitment sources. To enable a deeper investigation of behaviour we also constructed a survey that was sent to 2,714 members of Norstat’s internet panels.

    The statistical analysis includes contingency table analysis, multiple logistic regression, and Poisson regression. The results show that the demographic composition does not fully cover all the aspects of the Swedish population and some groups are less represented than others. The behaviour tends to differ between panel members that have responded to three or less surveys compared to members that have responded to twenty or more surveys. Source of recruitment does not seem to affect the results of studies, but it has some effect on the demographic composition of marketing research panels.

  • 63.
    Jonsson, Leif
    et al.
    Linköping University, Department of Computer and Information Science, PELAB - Programming Environment Laboratory. Ericsson AB, Sweden.
    Broman, David
    KTH Royal Institute Technology, Sweden; University of Calif Berkeley, CA USA.
    Magnusson, Måns
    Linköping University, Department of Computer and Information Science, Statistics. Linköping University, Faculty of Science & Engineering.
    Sandahl, Kristian
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Villani, Mattias
    Linköping University, Department of Computer and Information Science, Statistics. Linköping University, Faculty of Arts and Sciences.
    Eldh, Sigrid
    Ericsson AB, Sweden.
    Automatic Localization of Bugs to Faulty Components in Large Scale Software Systems using Bayesian Classification2016In: 2016 IEEE INTERNATIONAL CONFERENCE ON SOFTWARE QUALITY, RELIABILITY AND SECURITY (QRS 2016), IEEE , 2016, p. 425-432Conference paper (Refereed)
    Abstract [en]

    We suggest a Bayesian approach to the problem of reducing bug turnaround time in large software development organizations. Our approach is to use classification to predict where bugs are located in components. This classification is a form of automatic fault localization (AFL) at the component level. The approach only relies on historical bug reports and does not require detailed analysis of source code or detailed test runs. Our approach addresses two problems identified in user studies of AFL tools. The first problem concerns the trust in which the user can put in the results of the tool. The second problem concerns understanding how the results were computed. The proposed model quantifies the uncertainty in its predictions and all estimated model parameters. Additionally, the output of the model explains why a result was suggested. We evaluate the approach on more than 50000 bugs.

  • 64.
    Jonsson, Åsa
    et al.
    County Hospital Ryhov, Sweden.
    Hallberg, Ann-Charlotte
    Linköping University, Department of Computer and Information Science, Statistics. Linköping University, Faculty of Arts and Sciences.
    Edner, Magnus
    Karolinska University Hospital, Sweden.
    Lund, Lars H.
    Karolinska Institute, Sweden; Karolinska University Hospital, Sweden.
    Dahlström, Ulf
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Heart and Medicine Center, Department of Cardiology in Linköping.
    A comprehensive assessment of the association between anemia, clinical covariates and outcomes in a population-wide heart failure registry2016In: International Journal of Cardiology, ISSN 0167-5273, E-ISSN 1874-1754, Vol. 211, p. 124-131Article in journal (Refereed)
    Abstract [en]

    Background: The aim was to investigate the prevalence of, predictors of, and association with mortality and morbidity of anemia in a large unselected cohort of patients with heart failure (HF) and reduced ejection fraction (HFrEF) and to explore if there were specific subgroups of high risk. Methods: In patients with HFrEF in the Swedish Heart Failure Registry, we assessed hemoglobin levels and associations between baseline characteristics and anemia with logistic regression. Using propensity scores for anemia, we assessed the association between anemia and outcomes with Cox regression, and performed interaction and sub-group analyses. Results: There were 24 511 patients with HFrEF (8303 with anemia). Most important independent predictors of anemia were higher age, male gender and renal dysfunction. One-year survival was 75% with anemia vs. 81% without (p < 0.001). In the matched cohort after propensity score the hazard ratio associated with anemia was for all-cause death 1.34 (1.28-1.40; p < 0.0001), CV mortality 1.28 (1.20-1.36; p < 0.0001), and combined CV mortality or HF hospitalization 1.24 (1.18-1.30; p < 0.0001). In interaction analyses, anemia was associated with greater risk with lower age, male gender, EF 30-39%, and NYHA-class I-II. Conclusion: In HFrEF, anemia is associated with higher age, male gender and renal dysfunction and increased risk of mortality and morbidity. The influence of anemia on mortality was significantly greater in younger patients, in men, and in those with more stable HF. The clinical implication of these findings might be in the future to perform targeted treatment studies. (C) 2016 Elsevier Ireland Ltd. All rights reserved.

  • 65.
    Järvstråt, Lotta
    Linköping University, Department of Computer and Information Science, Statistics. Linköping University, The Institute of Technology.
    Functionality Classification Filter for Websites2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The objective of this thesis is to evaluate different models and methods for website classification. The websites are classified based on their functionality, in this case specifically whether they are forums, news sites or blogs. The analysis aims at solving a search engine problem, which means that it is interesting to know from which categories in a information search the results come.

    The data consists of two datasets, extracted from the web in January and April 2013. Together these data sets consist of approximately 40.000 observations, with each observation being the extracted text from the website. Approximately 7.000 new word variables were subsequently created from this text, as were variables based on Latent Dirichlet Allocation. One variable (the number of links) was created using the HTML-code for the web site.

    These data sets are used both in multinomial logistic regression with Lasso regularization, and to create a Naive Bayes classifier. The best classifier for the data material studied was achieved when using Lasso for all variables with multinomial logistic regression to reduce the number of variables. The  accuracy of this model is 99.70 %.

    When time dependency of the models is considered, using the first data to make the model and the second data for testing, the accuracy, however, is only 90.74 %. This indicates that the data is time dependent and that websites topics change over time.

  • 66.
    Kalish, Michael L.
    et al.
    Syracuse University, USA.
    Dunn, John C.
    University of Adelaide, Australia.
    Burdakov, Oleg P.
    Linköping University, Department of Mathematics, Optimization . Linköping University, Faculty of Science & Engineering.
    Sysoev, Oleg
    Linköping University, Department of Computer and Information Science, Statistics. Linköping University, Faculty of Arts and Sciences.
    A statistical test of the equality of latent orders2016In: Journal of mathematical psychology (Print), ISSN 0022-2496, E-ISSN 1096-0880, Vol. 70, p. 1-11, article id YJMPS2051Article in journal (Refereed)
    Abstract [en]

    It is sometimes the case that a theory proposes that the population means on two variables should have the same rank order across a set of experimental conditions. This paper presents a test of this hypothesis. The test statistic is based on the coupled monotonic regression algorithm developed by the authors. The significance of the test statistic is determined by comparison to an empirical distribution specific to each case, obtained via non-parametric or semi-parametric bootstrap. We present an analysis of the power and Type I error control of the test based on numerical simulation. Partial order constraints placed on the variables may sometimes be theoretically justified. These constraints are easily incorporated into the computation of the test statistic and are shown to have substantial effects on power. The test can be applied to any form of data, as long as an appropriate statistical model can be specified.

  • 67.
    Karanti, Alina
    et al.
    University of Gothenburg, Sweden.
    Bobeck, Christian
    Linköping University, Department of Computer and Information Science, Statistics. Linköping University, The Institute of Technology.
    Osterman, Maja
    Linköping University, Department of Computer and Information Science, Statistics. Linköping University, The Institute of Technology.
    Kardell, Mathias
    University of Gothenburg, Sweden.
    Tidemalm, Dag
    Karolinska Institute, Sweden.
    Runeson, Bo
    Karolinska Institute, Sweden.
    Lichtenstein, Paul
    Karolinska Institute, Sweden.
    Landen, Mikael
    University of Gothenburg, Sweden; Karolinska Institute, Sweden.
    Gender differences in the treatment of patients with bipolar disorder: A study of 7354 patients2015In: Journal of Affective Disorders, ISSN 0165-0327, E-ISSN 1573-2517, Vol. 174, p. 303-309Article in journal (Refereed)
    Abstract [en]

    Background: Gender differences in treatment that are not supported by empirical evidence have been reported in several areas of medicine. Here, the aim was to evaluate potential gender differences in the treatment for bipolar disorder. Methods: Data was collected from the Swedish National Quality Assurance Register for bipolar disorder (BipolaR). Baseline registrations from the period 2004-2011 of 7354 patients were analyzed. Multiple logistic regression analysis was used to study the impact of gender on interventions. Results: Women were more often treated with antidepressants, lamotrigine, electroconvulsive therapy, benzodiazepines, and psychotherapy. Men were more often treated with lithium. There were no gender differences in treatment with mood stabilizers as a group, neuroleptics, or valproate. Subgroup analyses revealed that ECT was more common in women only in the bipolar l subgroup. Contrariwise, lamotrigine was more common in women only in the bipolar II subgroup. Limitations: As BipolaR contains data on outpatient treatment of persons with bipolar disorder in Sweden, it is unclear if these Findings translate to inpatient care and to outpatient treatment in other countries. Conclusions: Men and women with bipolar disorder receive different treatments in routine clinical settings in Sweden. Gender differences in level of functioning, bipolar subtype, or severity of bipolar disorder could not explain the higher prevalence of pharmacological treatment, electroconvulsive therapy, and psychotherapy in women. Our results suggest that clinicians treatment decisions are to some extent unduly influenced by patients gender. (C) 2014 Elsevier B.V. All rights reserved.

  • 68.
    Karlsson, Jonas
    et al.
    Linköping University, Department of Computer and Information Science, Statistics. Linköping University, Faculty of Arts and Sciences.
    Karlsson, Roger
    Linköping University, Department of Computer and Information Science, Statistics. Linköping University, Faculty of Arts and Sciences.
    Inkrementell responsanalys: Vilka kunder bör väljas vid riktad marknadsföring?2013Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    If customers respond differently to a campaign, it is worthwhile to find those customers who respond most positively and direct the campaign towards them. This can be done by using so called incremental response analysis where respondents from a campaign are compared with respondents from a control group. Customers with the highest increased response from the campaign will be selected and thus may increase the company’s return. Incremental response analysis is applied to the mobile operator Tres historical data. The thesis intends to investigate which method that best explain the incremental response, namely to find those customers who give the highest incremental response of Tres customers, and what characteristics that are important.The analysis is based on various classification methods such as logistic regression, Lassoregression and decision trees. RMSE which is the root mean square error of the deviation between observed and predicted incremental response, is used to measure the incremental response prediction error. The classification methods are evaluated by Hosmer-Lemeshow test and AUC (Area Under the Curve). Bayesian logistic regression is also used to examine the uncertainty in the parameter estimates.The Lasso regression performs best compared to the decision tree, the ordinary logistic regression and the Bayesian logistic regression seen to the predicted incremental response. Variables that significantly affect the incremental response according to Lasso regression are age and how long the customer had their subscription.

  • 69.
    Khan, Muhammad Awais
    Linköping University, Department of Computer and Information Science, Statistics. Linköping University, The Institute of Technology.
    Isolating and quantifying factors affectingbody and paint business for Volvo Cars2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis focuses on identifying the degree of contribution of the most important factors affecting Body and Paint business of Volvo Car Corporation in Sweden. It is clear that Body and Paint business for VCCS directly depends on the number of registered accidents. Our major purpose is to determine the factors which have direct or indirect effect on reduction in the number of accidents in Sweden and to analyze in which degree they may affect the business. During the interviews with senior staff members, we discover that particularly city safety cars are mentioned by most of the specialists. Other important factors highlighted were mileage, weather, company car/ private car and age of a car.

     

    City Safety is a technology designed to help the driver mitigate, and in certain situations avoid, collisions at low speed by automatically bracking the vehicle. The estimated claim rate frequency i.e. claims per contract rate was 50% lower for city safety equipped; then other warranty cars models without system. The study also analysis the effect of rain, mean temperature and snow on Volvo Body part sales in Stockholm Sweden. Temperature snow impacted road accidents significantly. Snow was shown to be the leading variable, as the number of accidents increases sharply with increased snowfall. Temperature is the second important variable in the list i.e. as the temperature decreases by 1ͦC the sales of body and paint business in Stockholm increases by 1.6%.

     

    Time variable such as weekday, month, and year also plays significant role in this model. During Fridays 51% high accidents are expected then accidents occurred on Sundays.

  • 70.
    Klasson Svensson, Emil
    et al.
    Linköping University, Department of Computer and Information Science, Statistics.
    Persson, Anton
    Linköping University, Department of Computer and Information Science, Statistics.
    En statistisk analys av islastens effekt på en dammkonstruktion2016Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    A dam is a structure mainly used for storing water and generating electricity. The structure of a dam moves in a season-based pattern, mainly because of the difference in temperature between the air on outside of the dam and the water on the inside. Due to the Nordic climate, occurrences of icing on the water in the basin is fairly frequent. The effects of ice on the structural load of the dam are relatively unexplored and are the subject to this bachelor’s thesis.

    The goal of this project is to evaluate which predictors are significant to the movement of the dam with multiple linear regression models and dynamic regressions. The movement is measured by inverted pendulums that register the dam’s movement compared to the foundation. It is of particular interest to determine if the ice load influences the movement of the dam.

    The multiple regression models used to explain the dam’s movement were all discarded due to autocorrelation in the residuals. This falsifies the models, since autocorrelation means that they don’t meet the needed assumptions. To counteract the autocorrelation, dynamic models with autoregressive terms were fitted. These models showed no problem with autocorrelation.

    The result from the dynamic models were successful and managed to significantly explain the movement of the dam. The autoregressive terms proved to be efficient explanatory variables. The dynamic regression models also show that the time, temperature, hydrostatic pressure and ice thickness variables are also useful explanatory variables.

    The ice thickness shows a significant effect at the 5 % significance level on two of the investigated pendulums. The report's results indicate that there is reason to continue research on the ice load impact on dam constructions.

  • 71.
    Krook, Joakim
    et al.
    Linköping University, Department of Management and Engineering, Environmental Technique and Management . Linköping University, The Institute of Technology.
    Mårtensson, Anders
    Linköping University, Department of Management and Engineering, Environmental Technique and Management . Linköping University, The Institute of Technology.
    Eklund, Mats
    Linköping University, Department of Management and Engineering, Environmental Technique and Management . Linköping University, The Institute of Technology.
    Libiseller, Claudia
    Linköping University, Department of Computer and Information Science, Statistics. Linköping University, Faculty of Arts and Sciences.
    Swedish recovered wood waste: Linking regulation and contamination2008In: Waste Management, ISSN 0956-053X, E-ISSN 1879-2456, Vol. 28, no 3, p. 638-648Article in journal (Refereed)
    Abstract [en]

    In Sweden, large amounts of wood waste are generated annually from construction and demolition activities, but also from other discarded products such as packaging and furniture. A large share of this waste is today recovered and used for heat production. However, previous research has found that recovered wood waste (RWW) contains hazardous substances, which has significant implications for the environmental performance of recycling. Improved sorting is often suggested as a proper strategy to decrease such implications. In this study, we aim to analyse the impacts of waste regulation on the contamination of RWW. The occurrence of industrial preservative-treated wood, which contains several hazardous substances, was used as an indicator for contamination. First the management of RWW during 1995–2004 was studied through interviews with involved actors. We then determined the occurrence of industrial preservative-treated wood in RWW for that time period for each supplier (actor). From the results, it can be concluded that a substantially less contaminated RWW today relies on extensive source separation. The good news is that some actors, despite several obstacles for such upstream efforts, have already today proved capable of achieving relatively efficient separation. In most cases, however, the existing waste regulation has not succeeded in establishing strong enough incentives for less contaminated waste in general, nor for extensive source separation in particular. One important factor for this outcome is that the current market forces encourage involved actors to practice weak quality requirements and to rely on end-of-pipe solutions, rather than put pressure for improvements on upstream actors. Another important reason is that there is a lack of communication and oversight of existing waste regulations. Without such steering mechanisms, the inherent pressure from regulations becomes neutralized.

  • 72.
    Kullman, Eric
    et al.
    Linköping University, Department of Clinical and Experimental Medicine, Surgery. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Surgery in Östergötland.
    Frozanpor, Farshad
    Söder Sjukhuset, Stockholm.
    Söderlund, Claes
    Söder Sjukhuset, Stockholm.
    Linder, Stefan
    Söder Sjukhuset, Stockholm.
    Sandström, Per
    Linköping University, Department of Clinical and Experimental Medicine, Surgery. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Surgery, Orthopaedics and Cancer Treatment, Department of Surgery in Östergötland.
    Lindhoff-Larsson, Anna
    Östergötlands Läns Landsting.
    Toth, Ervin
    University Hospital MAS .
    Lindell, Gert
    University Hospital MAS.
    Jonas, Eduard
    Danderyd Hospital.
    Freedman, Jacob
    Danderyd Hospital.
    Ljungman, Martin
    Central Hospital Västerås.
    Rudberg, Claes
    Central Hospital Västerås.
    Ohlin, Bo
    Blekinge Hospital.
    Zacharias, Rebecka
    St Goran Hospital.
    Leijonmarck, Carl-Eric
    St Goran Hospital.
    Teder, Kalev
    Östergötlands Läns Landsting.
    Ringman, Anders
    Östergötlands Läns Landsting.
    Persson, Gunnar
    Ryhov Hospital.
    Gözen, Mehmet
    Västervik Hospital.
    Eriksson, Olle
    Linköping University, Department of Computer and Information Science, Statistics. Linköping University, Faculty of Arts and Sciences.
    Covered versus uncovered self-expandable nitinol stents in the palliative treatment of malignant distal biliary obstruction: results from a randomized, multicenter study2010In: GASTROINTESTINAL ENDOSCOPY, ISSN 0016-5107, Vol. 72, no 5, p. 915-923Article in journal (Refereed)
    Abstract [en]

    Background: Covered biliary metal stents have been developed to prevent tumor ingrowth. Previous comparative studies are limited and often include few patients. Objective: To compare differences in stent patency, patient survival, and complication rates between covered and uncovered nitinol stents in patients with malignant biliary obstruction. Design: Randomized, multicenter trial conducted between January 2006 and October 2008. Setting: Ten sites serving a total catchment area of approximately 2.8 million inhabitants. Patients: A total of 400 patients with unresectable distal malignant biliary obstruction. Interventions: ERCP with insertion of covered or uncovered metal stent. Follow-up conducted monthly for symptoms indicating stent obstruction. Main Outcome Measurements: Time to stent failure, survival time, and complication rate. Results: The patient survival times were 116 days (interquartile range 242 days) and 174 days (interquartile range 284 days) in the covered and uncovered stent groups, respectively (P = .320). The first quartile stent patency time was 154 days in the covered stent group and 199 days in the uncovered stent group (P = .326). There was no difference in the incidence of pancreatitis or cholecystitis between the 2 groups. Stent migration occurred in 6 patients (3%) in the covered group and in no patients in the uncovered group (P = .030). Limitations: Randomization was not blinded. Conclusions: There were no significant differences in stent patency time, patient survival time, or complication rates between covered and uncovered nitinol metal stents in the palliative treatment of malignant distal biliary obstruction. However, covered stents migrated significantly more often compared with uncovered stents, and tumor ingrowth was more frequent in uncovered stents.

  • 73.
    Li, Feng
    et al.
    Stockholm University, Sweden .
    Villani, Mattias
    Linköping University, Department of Computer and Information Science, Statistics. Linköping University, Faculty of Arts and Sciences.
    Efficient Bayesian Multivariate Surface Regression2013In: Scandinavian Journal of Statistics, ISSN 0303-6898, E-ISSN 1467-9469, Vol. 40, no 4, p. 706-723Article in journal (Refereed)
    Abstract [en]

    Methods for choosing a fixed set of knot locations in additive spline models are fairly well established in the statistical literature. The curse of dimensionality makes it nontrivial to extend these methods to nonadditive surface models, especially when there are more than a couple of covariates. We propose a multivariate Gaussian surface regression model that combines both additive splines and interactive splines, and a highly efficient Markov chain Monte Carlo algorithm that updates all the knot locations jointly. We use shrinkage prior to avoid overfitting with different estimated shrinkage factors for the additive and surface part of the model, and also different shrinkage parameters for the different response variables. Simulated data and an application to firm leverage data show that the approach is computationally efficient, and that allowing for freely estimated knot locations can offer a substantial improvement in out-of-sample predictive performance.

  • 74.
    Liu, Wenjie
    Linköping University, Department of Computer and Information Science, Statistics. Linköping University, The Institute of Technology.
    Estimation and bias correction of the magnitude of an abrupt level shift2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Consider a time series model which is stationary apart from a single shift in mean. If the time of a level shift is known, the least squares estimator of the magnitude of this level shift is a minimum variance unbiased estimator. If the time is unknown, however, this estimator is biased. Here, we first carry out extensive simulation studies to determine the relationship between the bias and three parameters of our time series model: the true magnitude of the level shift, the true time point and the autocorrelation of adjacent observations. Thereafter, we use two generalized additive models to generalize the simulation results. Finally, we examine to what extent the bias can be reduced by multiplying the least squares estimator with a shrinkage factor. Our results showed that the bias of the estimated magnitude of the level shift can be reduced when the level shift does not occur close to the beginning or end of the time series. However, it was not possible to simultaneously reduce the bias for all possible time points and magnitudes of the level shift.

  • 75.
    Maghazeh, Arian
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Bordoloi, Unmesh D.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Villani, Mattias
    Linköping University, Department of Computer and Information Science, Statistics. Linköping University, Faculty of Science & Engineering.
    Eles, Petru
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Peng, Zebo
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Perception-aware power management for mobile games via dynamic resolution scaling2015In: 2015 IEEE/ACM INTERNATIONAL CONFERENCE ON COMPUTER-AIDED DESIGN (ICCAD), IEEE , 2015, p. 613-620Conference paper (Refereed)
    Abstract [en]

    Modern mobile devices provide ultra-high resolutions in their display panels. This imposes ever increasing workload on the GPU leading to high power consumption and shortened battery life. In this paper, we first show that resolution scaling leads to significant power savings. Second, we propose a perception-aware adaptive scheme that sets the resolution during game play. We exploit the fact that game players are often willing to trade quality for longer battery life. Our scheme uses decision theory, where the predicted user perception is combined with a novel asymmetric loss function that encodes users' alterations in their willingness to save power.

  • 76.
    Mahfouzi, Rouhollah
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Aminifar, Amir
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering. École Polytechnique Fédérale de Lausanne (EPFL), Switzerland.
    Eles, Petru
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Peng, Zebo
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Villani, Mattias
    Linköping University, Department of Computer and Information Science, Statistics. Linköping University, Faculty of Arts and Sciences.
    Intrusion-Damage Assessment and Mitigation in Cyber-Physical Systems for Control Applications2016In: RTNS '16 Proceedings of the 24th International Conference on Real-Time Networks and Systems, New York: ACM Press, 2016, p. 141-150Conference paper (Refereed)
    Abstract [en]

    With cyber-physical systems opening to the outside world, security can no longer be considered a secondary issue. One of the key aspects in security of cyber-phyiscal systems is to deal with intrusions. In this paper, we highlight the several unique properties of control applications in cyber-physical systems. Using these unique properties, we propose a systematic intrusion-damage assessment and mitigation mechanism for the class of observable and controllable attacks.

    On the one hand, in cyber-physical systems, the plants follow certain laws of physics and this can be utilized to address the intrusion-damage assessment problem. That is, the states of the controlled plant should follow those expected according to the physics of the system and any major discrepancy is potentially an indication of intrusion. Here, we use a machine learning algorithm to capture the normal behavior of the system according to its dynamics. On the other hand, the control performance strongly depends on the amount of allocated resources and this can be used to address the intrusion-damage mitigation problem. That is, the intrusion-damage mitigation is based on the idea of allocating more resources to the control application under attack. This is done using a feedback-based approach including a convex optimization.

  • 77.
    Malmborg, Jonas
    et al.
    National Forens Centre, Chemistry and Technology, SE-58194 Linkoping, Sweden.
    Nordgaard, Anders
    Linköping University, Department of Computer and Information Science, Statistics. Linköping University, Faculty of Arts and Sciences. National Forens Centre, Chemistry and Technology, SE-58194 Linkoping, Sweden.
    Forensic characterization of mid-range petroleum distillates using light biomarkers2016In: Environmental Forensics, ISSN 1527-5922, E-ISSN 1527-5930, Vol. 17, no 3, p. 244-252Article in journal (Refereed)
    Abstract [en]

    Due to oil refining, commonly used higher boiling biomarkers for oil-source correlation are absent from mid-range petroleum distillates, while lighter biomarkers are concentrated in such products. This study evaluated 63 diagnostic ratios of light biomarkers such as bicyclic sesquiterpanes, diamondoids, and lighter aromatic compounds using 70 diesel oil samples obtained from three Swedish refineries and local gas stations, mostly over a six-month period in 2015. On the basis of their diagnostic power and partial correlation coefficients, a set of 24 ratios is suggested for oil-source correlation of lighter products. The frequency of false positives for this set was determined to be approximately 0.1%. It should be emphasized that in the event of an oil spill, diesel oils are rapidly influenced by weathering and many of the ratios will be affected.

  • 78.
    Mansoor, Shaheer
    Linköping University, Department of Computer and Information Science, Statistics. Linköping University, The Institute of Technology.
    System Surveillance2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In recent years, trade activity in stock markets has increased substantially. This is mainly attributed to the development of powerful computers and intranets connecting traders to markets across the globe. The trades have to be carried out almost instantaneously and the systems in place that handle trades are burdened with millions of transactions a day, several thousand a minute. With increasing transactions the time to execute a single trade increases, and this can be seen as an impact on the performance. There is a need to model the performance of these systems and provide forecasts to give a heads up on when a system is expected to be overwhelmed by transactions. This was done in this study, in cooperation with Cinnober Financial Technologies, a firm which provides trading solutions to stock markets. To ensure that the models developed weren‟t biased, the dataset was cleansed, i.e. operational and other transactions were removed, and only valid trade transactions remained. For this purpose, a descriptive analysis of time series along with change point detection and LOESS regression were used. State space model with Kalman Filtering was further used to develop a time varying coefficient model for the performance, and this model was applied to make forecasts. Wavelets were also used to produce forecasts, and besides this high pass filters were used to identify low performance regions. The State space model performed very well to capture the overall trend in performance and produced reliable forecasts. This can be ascribed to the property of Kalman Filter to handle noisy data well. Wavelets on the other hand didn‟t produce reliable forecasts but were more efficient in detecting regions of low performance.

  • 79.
    Mattsson, Linn
    et al.
    Linköping University, Department of Computer and Information Science, Statistics.
    Wass, Martin
    Linköping University, Department of Computer and Information Science, Statistics.
    Prognoser för hotellmarknaden i Stockholm2016Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Background: This thesis targets hotels in Stockholm with aggregated data for the city. In the hotel market there’s three key indicators of particular interest and can be said describes how the market goes. Because of how much influence these key indicator have on the hotels it’s in great interest for the hotels to compare themselves with the market values. If these key indicators where forecasted it would perhaps be of great interest for the hotels to buy these forecasts to be able to control the room pricing in advance.

    Purpose: Develop forecasting models due to future event and bookings with occupancy and room revenue as response variables. The key indicators revenue per available rooms and average price is then calculated through these forecasts for the year 2016.

    Method: Since data consist of response variables (called output series) where the future values this series depends on past values of this series and a multiple set of related time series and external events (called input series) a dynamic regression called “regression with ARMA errors” where used. The method implies that you suit a multiple regression where the error terms are modelled with an appropriate ARMA model.

    Results: The model for occupancy consist of four dependent variables and the model for the room revenue contain seven dependent variables. The error terms for these models include an autoregressive model with both seasonal and non-seasonal orders.

    The forecast for the key indicators seems to follow the same pattern as previous years, where the event type Event more often than not gives a high estimate in relation to the current month. The event type Holiday seems to have a negative impact and bookings has a small positive effect for both models.

    Conclusions: The models seems to fit data well but the input series needs more processing where the variable event seems to need some subgrouping. To forecast the room revenue is seems like a variable explaining price changes need to be constructed.

  • 80.
    Mikiver, Rasmus
    et al.
    Linköping University, Department of Computer and Information Science, Statistics.
    Andersson, Rasmus
    Linköping University, Department of Computer and Information Science, Statistics.
    Ungdomars attityder till att köra mopedonyktra2012Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The overall objective of this report was to examine what affect young moped driver’s intentions to drive after drinking alcohol. A further aim was to illustrate Swedish adolescent’s attitudes towards alcohol and traffic in general. All results and analysis are based on a survey created by Swedish National Road and Transport Research Institute (VTI). The survey was addressed to high school students and the analysis consisted of answers from 1 933 students in the age of 15 - 21 years.

    The statistical analysis included χ2-tests as well as an ordinal logistic regression model. The results showed that adolescents in general thought it was an unacceptable behavior to drink and drive. However, the extent of expected acceptance level was higher when assessing their friend’s opinion. What proved to be most essential for the adolescent’s intentions was how likely they considered it to be that their best friends would drive in the same situation. The results also showed that a person with earlier experience of driving a moped with influence of alcohol or drugs has a clearly higher intention to drink and drive again.

  • 81.
    Minya, Kristoffer
    Linköping University, Department of Computer and Information Science, Statistics. Linköping University, The Institute of Technology.
    Överlevnadsanalys i tjänsteverksamhet: Tidspåverkan i överklagandeprocessen på Migrationsverket2014Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The Swedish Migration Board is an agency that review applications from individuals who wish to seek shelter, have citizenship, study or want to work in Sweden. In recent time there has been a large increase in applications and the time for which a decision is made has increased. Each type of application (such as citizenship) is a process consisting of several stages. How the decision is going through these steps is called flow. The Swedish Migration Board would therefore like to increase their flow efficiency. When the decision is made and the person has take part of it but is not satisfied, he can appeal. This is one of the most complex processes at the Board. The aim is to analyze how long this process will take and what steps in the process affects the time. One step (which was later found to have a significant effect on time) is opinions. This is when the court requests information on what the person is appealing has to say about why he is appealing. To analyze this, two methods were relevant, accelerated failure time (AFT) and the multi-state models (MSM). One can predict time to event (AFT), the other to analyze the effect of time-manipulation (MSM) in the flow. Opinions early in the process is crucial to how quickly an appeal get judgment while the number of opinions increases the time enormously. There are other factors that affect the time but not so much as opinions. The flow efficiency can be increased by taking time to write an informative opinion which allows the court need not to ask for more opinions.

  • 82.
    Månsson Vogel, Andreas
    et al.
    Linköping University, Department of Computer and Information Science, Statistics.
    Spreco, Armin
    Linköping University, Department of Computer and Information Science, Statistics.
    En modell för väderjustering av cykelflöden2009Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
    Abstract [sv]

    Vectura är ett företag vars verksamhet är koncentrerad till transportinfrastruktur och deras mål är att hitta bättre lösningar för infrastrukturen. En stor del av trafikanterna i Sverige använder cykeln som transportmedel men cyklingen är i hög grad beroende av vädret som varierar hela tiden. Det varierande vädret gör det svårt att se hur cyklingen förändras över tiden och för att kunna se denna förändring behövs en modell som rensar cykelflödet från vädrets påverkan.

    Syftet med denna rapport är just att utveckla en sådan modell. Denna modell ska tas fram med hjälp av dels cykelflödesdata och dels väderdata från ett antal gator i städer runt om i Sverige och ska vara tillämpbar överallt i landet.

    Metoden som används för att ta fram modellen är multiplikativ tidsserieregression. Då syftet är att ta fram en rikstäckande modell måste en gemensam variabeluppsättning väljas som vi ska använda oss av när vi anpassar regressionskoefficienterna för varje gata. Detta variabelval gör vi med hjälp av

    P-värden från individuella t-test och Akaikes informationskriterium. När lämpliga variabler har valts ut anpassas en separat regressionsmodell med dessa variabler för varje gata och därefter vägs betaskattningarna samman så att vi får en allmän modell. För att validera modellen utför vi en korsvalidering som går ut på att utelämna en av städerna när vi väger samman betaskattningarna och sedan testa den nya modellen på någon gata i den utelämnade staden.

    Resultaten visar att modellen som vi utvecklat kan användas som en allmän modell för Sverige. Dels reducerar modellen standardavvikelsen för cykelflödet tillfredsställande och dels fungerar korsvalideringen bra. Modellen är utvecklad så att man ska kunna justera bort antingen endast vädereffekter från cykelflödet eller, utöver vädereffekter, justera bort även kalendereffekter och periodiska effekter från cykelflödet.

  • 83.
    Mészáros, Gábor
    et al.
    University of Natural Resources and Life Sciences, Vienna, Austria.
    Eaglen, Sophie
    University of Natural Resources and Life Sciences, Vienna, Austria.
    Waldmann, Patrik
    Linköping University, Department of Computer and Information Science, Statistics. Linköping University, The Institute of Technology.
    Sölkner, Johann
    University of Natural Resources and Life Sciences, Vienna, Austria.
    A genome wide association study for longevity in cattle2014In: Open Journal of Genetics, ISSN 2162-4453, E-ISSN 2162-4461, Vol. 4, no 1, p. 46-55Article in journal (Refereed)
    Abstract [en]

    Longevity is regarded as the most important functional trait in cattle breeding with high economic value yet low heritability. In order to identify genomic regions associated with longevity, a genome wise association study was performed using data from 4887 Fleckvieh bulls and 33,556 SNPs after quality control. Single SNP regression was used for identification of important SNPs including eigenvectors as a means of correction for population structure. SNPs selected with a false discovery rate threshold of 0.05 and with local false discovery rate identified genomic regions associated with longevity which were subsequently cross checked with the National Center for Biotechnology Information (NCBI) database. This, to identify interesting genes in cattle and their homologue forms in other species. The most notable genes were SYT10 located on chromosome 5, ADAMTS3 on chromosome 6, NTRK2 on chromosome 8 and SNTG1 on chromosome 14 of the cattle genome. Several of the genes found have previously been associated with cattle fertility. Poor fertility is an important culling reason and thereby affects longevity in cattle. Several signals were located in regions sparse with described genes, which suggest that there might be several other non-identified genetic pathways for this important trait.

  • 84.
    Nalenz, Malte
    Linköping University, Department of Computer and Information Science, Statistics.
    Horseshoe RuleFit: Learning Rule Ensembles via Bayesian Regularization2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This work proposes Hs-RuleFit, a learning method for regression and classification, which combines rule ensemble learning based on the RuleFit algorithm with Bayesian regularization through the horseshoe prior. To this end theoretical properties and potential problems of this combination are studied. A second step is the implementation, which utilizes recent sampling schemes to make the Hs-RuleFit computationally feasible. Additionally, changes to the RuleFit algorithm are proposed such as Decision Rule post-processing and the usage of Decision rules generated via Random Forest.

    Hs-RuleFit addresses the problem of finding highly accurate and yet interpretable models. The method shows to be capable of finding compact sets of informative decision rules that give a good insight in the data. Through the careful choice of prior distributions the horse-shoe prior shows to be superior to the Lasso in this context. In an empirical evaluation on 16 real data sets Hs-RuleFit shows excellent performance in regression and outperforms the popular methods Random Forest, BART and RuleFit in terms of prediction error. The interpretability is demonstrated on selected data sets. This makes the Hs-RuleFit a good choice for science domains in which interpretability is desired.

    Problems are found in classification, regarding the usage of the horseshoe prior and rule ensemble learning in general. A simulation study is performed to isolate the problems and potential solutions are discussed.

    Arguments are presented, that the horseshoe prior could be a good choice in other machine learning areas, such as artificial neural networks and support vector machines.

  • 85.
    Nichols, Thomas E.
    et al.
    University of Warwick, England.
    Eklund, Anders
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Biomedical Engineering, Medical Informatics. Linköping University, Department of Computer and Information Science, Statistics. Linköping University, Faculty of Science & Engineering.
    Knutsson, Hans
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Biomedical Engineering, Medical Informatics. Linköping University, Faculty of Science & Engineering.
    A defense of using resting state fMRI as null data for estimating false positive rates2017In: Cognitive Neuroscience, ISSN 1758-8928, E-ISSN 1758-8936, Vol. 8, no 3, p. 144-145Article in journal (Refereed)
    Abstract [en]

    A recent Editorial by Slotnick (2017) reconsiders the findings of our paper on the accuracy of false positive rate control with cluster inference in fMRI (Eklund et al, 2016), in particular criticising our use of resting state fMRI data as a source for null data in the evaluation of task fMRI methods. We defend this use of resting fMRI data, as while there is much structure in this data, we argue it is representative of task data noise and such analysis software should be able to accommodate this noise. We also discuss a potential problem with Slotnick’s own method.

  • 86.
    Nilsson, Mattias
    Linköping University, Department of Computer and Information Science, Statistics.
    Förändringar i Ålands omsättningsindex: Val av ledande förklarande variabler och undersökning av de branschindex som ingår2010Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Denna uppsats har gjorts på uppdrag av Ålands statistik- och utredningsbyrå (ÅSUB) i syfte att förklara och prognostisera de åländska företagens omsättningsutveckling över tiden.

    I uppsatsen har jag undersökt om en tidigare framtagen modell för att förklara Ålands omsättningsindex kan användas för att förklara olika branschindex på Åland.

    Jag har även tagit fram två olika modeller på ledande indikatorer från Sverige och Finland med ARIMA-feltermer. De ledande indikatorerna är svenska och finska konsumenters förtroendeindex samt industrins förtroendeindex och svenska OMX 30 börsindex. Modellerna använder olika fördröjningar på dessa fem indikatorer som förklaringsvariabler. Modell 1 använder utvalda fördröjningar och Modell 2 använder glidande medelvärden på fördröjningsintervall.

    Jag har testat hur bra de två modellerna kan förklara och prognostisera Ålands omsättningsindex och de olika branschindexen. Båda modellerna förklarar Ålands omsättningsindex bra. Modell 2 är klart bättre än Modell 1 på att förklara de olika branschindexen. Prognosförmågan för båda modellerna är diskutabel. Modell 2 är bättre än Modell 1 på att prognostisera både Ålands omsättningsindex och dess branschindex.

    Jag har visat att det går att ta fram en bra modell för att förklara Ålands omsättningsindex och dess branschindex med hjälp av ledande indikatorer från Sverige och Finland. 

  • 87.
    Norberg, Pernilla
    et al.
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    Persson, H Lennart
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Respiratory Medicine.
    Schmekel, Birgitta
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Clinical Physiology in Linköping.
    Alm Carlsson, Gudrun
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Faculty of Health Sciences.
    Wahlin, Karl
    Linköping University, Department of Computer and Information Science, Statistics. Linköping University, Faculty of Arts and Sciences.
    Sandborg, Michael
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    Gustafsson, Agnetha
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    Does quantitative lung SPECT detect lung abnormalities earlier than lung function tests?: Results of a pilot study2014In: EJNMMI Research, ISSN 2191-219X, E-ISSN 2191-219X, Vol. 4, no 39, p. 1-12Article in journal (Refereed)
    Abstract [en]

    Background: Heterogeneous ventilation in lungs of allergic individuals, cigarette smokers, asthmatics and chronic obstructive pulmonary disease (COPD) patients has been demonstrated using imaging modalities such as PET, MR and SPECT. These individuals suffer from narrow and/or closed airways to various extents. By calculating regional heterogeneity in lung ventilation SPECT images as the coefficient of variation (CV) in small elements of the lung, heterogeneity maps and CV-frequency curves can be generated and used to quantitatively measure heterogeneity. This work explores the potential to use such measurements to detect mild ventilation heterogeneities in lung healthy subjects.

    Method: Fourteen healthy subjects without documented lung disease or respiratory symptoms, and two patients with documented airway disease, inhaled on average approximately 90 MBq 99mTc-Technegas immediately prior to the 20 min SPECT acquisition. Variation in activity uptake between subjects was compensated for in resulting CV values. The area under the compensated CV frequency curve (AUC), for CV values greater than a threshold value CVT, AUC(CV> CVT), was used as the measure of ventilation heterogeneity.

    Results: Patients with lung function abnormalities, according to lung function tests, generated higher AUC(CV>20%) values compared to healthy subjects (p=0.006). Strong linear correlations with the AUC(CV>20%) values were found for age (p=0.006) and height (p=0.001). These demonstrated that ventilation heterogeneities increased with age and that they depend on lung size. Strong linear correlations were found for the lung function value related to indices of airway closure/air trapping, RV/TLC (p=0.009), and DLCOc (p=0.009), a value partly related to supposed ventilation/perfusion mismatch. These findings support the association between conventional lung function tests and the AUC(CV>20%) value.

    Conclusions: Among the healthy subjects there is a group with increased AUC(CV>20%) values, but with normal lung function tests, which implies that it might be possible to differentiate ventilation heterogeneities earlier in a disease process than by lung function tests.

  • 88.
    Nordfors, Per
    Linköping University, Department of Computer and Information Science, Statistics. Linköping University, Faculty of Science & Engineering.
    Prediction of Code Lifetime2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    There are several previous studies in which machine learning algorithms are used to predict how fault-prone a piece of code is. This thesis takes on a slightly different approach by attempting to predict how long a piece of code will remain unmodified after being written (its “lifetime”). This is based on the hypothesis that frequently modified code is more likely to contain weaknesses, which may make lifetime predictions useful for code evaluation purposes. In this thesis, the predictions are made with machine learning algorithms which are trained on open source code examples from GitHub. Two different machine learning algorithms are used: the multilayer perceptron and the support vector machine. A piece of code is described by three groups of features: code contents, code properties obtained from static code analysis, and metadata from the version control system Git. In a series of experiments it is shown that the support vector machine is the best performing algorithm and that all three feature groups are useful for predicting lifetime. Both the multilayer perceptron and the support vector machine outperform a baseline prediction which always outputs the mean lifetime of the training set. This indicates that lifetime to some extent can be predicted based on information extracted from the code. However, lifetime prediction performance is shown to be highly dataset dependent with large error magnitudes.

  • 89.
    Nordgaard, Anders
    Linköping University, Department of Computer and Information Science, Statistics. Linköping University, Faculty of Arts and Sciences. Polismyndigheten - Nationellt Forensiskt Centrum.
    Activity level and evaluative reports on forensic science evidence2013Conference paper (Other academic)
  • 90.
    Nordgaard, Anders
    Linköping University, Department of Computer and Information Science, Statistics. Linköping University, Faculty of Arts and Sciences.
    Challenges in forensic evidence evaluation2012Conference paper (Other academic)
    Abstract [en]

    Interpretation andevaluation of forensic evidence is in essence a matter of probabilistic reasoning.The absence of models and sufficient background databases designed specificallyfor each particular forensic case make it a challenge to pursue such reasoning.However, with a coherent framework it is possible to reason with subjectiveprobabilities (subjective in the sense that they depend on the expert’sexperience and general knowledge) without leaving the court with a statementthat is merely the expert’s personal opinion. Bayesian reasoning, through theuse of Bayes factors (or very often likelihood ratios) constitutes such aframework. Here we present how the use of an ordinal scale for the Bayes factorcan allay the fear of subjectivity, and also how it can ease the problem ofevaluating evidence when there are multiple explanations for the forensicfindings with different likelihoods.

  • 91.
    Nordgaard, Anders
    Linköping University, Department of Computer and Information Science, Statistics. Linköping University, Faculty of Arts and Sciences.
    Construction of a scale of conclusions and its use for all types of forensic evidence2011Conference paper (Other (popular science, discussion, etc.))
  • 92.
    Nordgaard, Anders
    Linköping University, Department of Computer and Information Science, Statistics. Linköping University, Faculty of Arts and Sciences. Swedish Police Author, National Forens Centre, SE-58194 Linkoping, Sweden.
    Editorial Material: Comment on Dismissal of the illusion of uncertainty on the assessment of a likelihood ratio by Taroni F., Bozza S., Biederman A. and Aitken C.(1) in LAW PROBABILITY and RISK, vol 15, issue 1, pp 17-222016In: Law, Probability and Risk, ISSN 1470-8396, E-ISSN 1470-840X, Vol. 15, no 1, p. 17-22Article in journal (Other academic)
    Abstract [en]

    n/a

  • 93.
    Nordgaard, Anders
    Linköping University, Department of Computer and Information Science, Statistics. Linköping University, Faculty of Arts and Sciences.
    Hållbar utveckling - aktuella statistiska utmaningar och problem i arbetet med miljöfrågor och utvecklingsövervakning2008In: Statistisk metod & analys - Skarpsynt utredning genom träffsäker datainsamling, IQPC, Stockholm, Sweden, 2008Conference paper (Other (popular science, discussion, etc.))
  • 94.
    Nordgaard, Anders
    Linköping University, Department of Computer and Information Science, Statistics. Linköping University, Faculty of Arts and Sciences. Polismyndigheten - Nationellt Forensiskt Centrum.
    Interpreting findings – evaluation and conclusions about what happened at the crime scene2014Conference paper (Other (popular science, discussion, etc.))
  • 95.
    Nordgaard, Anders
    Linköping University, Department of Computer and Information Science, Statistics. Linköping University, Faculty of Arts and Sciences.
    Resampling species-wise collected abundance data for flexible assessment of changes in biodiversity2007In: Bulletin of the ISI - Volume LXII: PROCEEDINGS, Lisboa, Portugal, 22-29 August 2007 / [ed] Gomes M.I.,Pinto Martins J.A.,Silva J.A., 2007, p. 1596-1603Conference paper (Other academic)
  • 96.
    Nordgaard, Anders
    Linköping University, Department of Computer and Information Science, Statistics. Linköping University, Faculty of Arts and Sciences. Polismyndigheten - Nationellt Forensiskt Centrum.
    Värdering och rapportering av forensiska resultat vid SKL2014Conference paper (Other (popular science, discussion, etc.))
  • 97.
    Nordgaard, Anders
    et al.
    Linköping University, Department of Computer and Information Science, Statistics. Linköping University, Faculty of Arts and Sciences. Polismyndigheten - Nationellt Forensiskt Centrum.
    Andersson, Kjell
    Polismyndigheten - Nationellt Forensiskt Centrum.
    Högberg, Carina
    Polismyndigheten - Nationellt Forensiskt Centrum.
    The Multivariate Kernel Likelihood Ratio Method Applied on Comparison of Amphetamine Seizures2014Conference paper (Other academic)
    Abstract [en]

    Comparison of seizures of amphetamine with respect to their origins of illicit manufacturing can be done by investigating the amphetamine impurity pattern. Such an impurity pattern is a result of an incomplete cleaning-up process – typical for illicit manufacturing – when producing the drug. The manufacturing process can be divided into three steps: (1) choosing a recipe for how to produce; (2) producing amphetamine oil; and finally (3) precipitating the amphetamine from the oil.

    The impurity pattern of the amphetamine will depend on the recipe itself, the conditions used for the synthesis, the precipitation process and the method of cleaning-up. The impurity profile is a chromatogram of around 150 different contaminants, of these contaminants 26 have been used by several European countries in police intelligence work to link manufacturers of illicit drugs [1]. However, the linkage methods used are investigative and not evaluative.   

    The issue addressed when two specific seizures are to be compared, and the results are going to be used in the court of law, is whether they originate from the same precipitation batch.  When this is true the impurity patterns of the two seizures are in general expected to be similar, at least for stable contaminants. This is a less expected result if the seizures originate from different batches.

    Interpretation of observed similarities and differences between the impurity patterns of two seizures is still to a large extent based on subjective judgements where in Sweden the experiences of two forensic experts are used. In this presentation we show how the so-called multivariate kernel likelihood ratio approach [2] can be used for this interpretation. From a designed experiment comprising several recipes, the variance components for a subset or for a lower-dimensional projection of all contaminants are estimated and likelihood ratios can then be easily calculated. A cross-validatory study shows high sensitivity as well as high specificity of the likelihood ratios.

  • 98.
    Nordgaard, Anders
    et al.
    Linköping University, Department of Computer and Information Science, Statistics. Linköping University, Faculty of Arts and Sciences.
    Ansell, Ricky
    Linköping University, Department of Physics, Chemistry and Biology, Molecular genetics. Linköping University, The Institute of Technology.
    Drotz, Weine
    Statens Kriminaltekniska Laboratorium.
    Jaeger, Lars
    Statens Kriminaltekniska Laboratorium.
    Scale of conclusions for the value of evidence2012In: Law, Probability and Risk, ISSN 1470-8396, E-ISSN 1470-840X, Vol. 11, no 1, p. 1-24Article in journal (Refereed)
    Abstract [en]

    Scales of conclusion in forensic interpretation play an important role in the interface between scientific work at a forensic laboratory and different bodies of the jurisdictional system of a country. Of particular importance is the use of a unified scale that allows interpretation of different kinds of evidence in one common framework. The logical approach to forensic interpretation comprises the use of the likelihood ratio as a measure of evidentiary strength. While fully understood by forensic scientists, the likelihood ratio may be hard to interpret for a person not trained in natural sciences or mathematics. Translation of likelihood ratios to an ordinal scale including verbal counterparts of the levels is therefore a necessary procedure for communicating evidence values to the police and in the courtroom. In this paper, we present a method to develop an ordinal scale for the value of evidence that can be applied to any type of forensic findings. The method is built on probabilistic reasoning about the interpretation of findings and the number of scale levels chosen is a compromise between a pragmatic limit and mathematically well-defined distances between levels. The application of the unified scale is illustrated by a number of case studies.

  • 99.
    Nordgaard, Anders
    et al.
    Linköping University, Department of Computer and Information Science, Statistics. Linköping University, Faculty of Arts and Sciences. Polismyndigheten - Nationellt Forensiskt Centrum.
    Ansell, Ricky
    Linköping University, Department of Physics, Chemistry and Biology, Biology. Linköping University, Faculty of Science & Engineering.
    Hedell, Ronny
    Polismyndigheten - Nationellt Forensiskt Centrum.
    ’Blame the brother’-Assessment of forensic DNA evidence when alternative explanations have different likelihoods2011Conference paper (Other academic)
    Abstract [en]

    In a crime case where a suspect is assumed to be the donor of a recovered stain, forensic DNA evidence presented in terms of a likelihood ratio is a clear course as long as the set of alternative donors contains no close relative of the suspect, since the latter has a higher likelihood than has an individual unrelated to the suspect. The state-of-art today at several laboratories is to report the likelihood ratio but with a reservation stating its lack of validity if the stain originates from a close relative. Buckleton et al[†] derived a so-called extended likelihood ratio for reporting DNA evidence values when a full sibling is present in the set of potential alternative donors. This approach requires consideration of prior probabilities for each of the alternative donors to be the source of the stain and may therefore be problematic to apply in practice. Here we present an alternative way of using prior probabilities in the extended likelihood ratio when the latter is reported on an ordinal scale of conclusions. Our example show that for a 12 STR-marker profile using the extended likelihood ratio approach would not imply a change in the level reported compared to the ordinary likelihood ratio approach, unless the close relative has a very high prior probability of being the donor compared to an unrelated individual.

    [†] Buckleton JS, Triggs CM, Champod C., Science & Justice 46: 69-78.

     

  • 100.
    Nordgaard, Anders
    et al.
    Linköping University, Department of Computer and Information Science, Statistics. Linköping University, Faculty of Arts and Sciences.
    Ansell, Ricky
    Linköping University, Department of Physics, Chemistry and Biology, Molecular genetics .
    Jaeger, Lars
    Swedish National Laboratory of Forensic Sciences, Linköping, Sweden.
    Drotz, Weine
    Swedish National Laboratory of Forensic Sciences, Linköping, Sweden.
    Ordinal scales of conclusions for the value of evidence2009In: 5th European Academy of Forensic Science Conference, Glasgow, UK, 2009Conference paper (Other academic)
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