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In search of justification for the unpredictability paradox
KTH, School of Architecture and the Built Environment (ABE), Philosophy and History of Technology, Philosophy.ORCID iD: 0000-0001-9730-2133
2014 (English)In: Trials, ISSN 1745-6215, Vol. 15, no 480Article in journal, Editorial material (Refereed) Published
Abstract [en]

A 2011 Cochrane Review found that adequately randomized trials sometimes revealed larger, sometimes smaller, and often similar effect sizes to inadequately randomized trials. However, they found no average statistically significant difference in effect sizes between the two study types. Yet instead of concluding that adequate randomization had no effect the review authors postulated the "unpredictability paradox", which states that randomized and non-randomized studies differ, but in an unpredictable direction. However, stipulating the unpredictability paradox is problematic for several reasons: 1) it makes the authors' conclusion that adequate randomization makes a difference unfalsifiable-if it turned out that adequately randomized trials had significantly different average results from inadequately randomized trials the authors could have pooled the results and concluded that adequate randomization protected against bias; 2) it leaves other authors of reviews with similar results confused about whether or not to pool results (and hence which conclusions to draw); 3) it discourages researchers from investigating the conditions under which adequate randomization over- or under-exaggerates apparent treatment benefits; and 4) it could obscure the relative importance of allocation concealment and blinding which may be more important than adequate randomization.

Place, publisher, year, edition, pages
BioMed Central, 2014. Vol. 15, no 480
Keyword [en]
Random allocation, Randomized controlled trial, Meta-analysis, Evidence-based medicine
National Category
Medical and Health Sciences
URN: urn:nbn:se:kth:diva-159121DOI: 10.1186/1745-6215-15-480ISI: 000346877200001ScopusID: 2-s2.0-84925140323OAI: diva2:783834

QC 20150127

Available from: 2015-01-27 Created: 2015-01-22 Last updated: 2015-03-12Bibliographically approved
In thesis
1. Philosophical controversies in the evaluation of medical treatments: With a focus on the evidential roles of randomization and mechanisms in Evidence-Based Medicine
Open this publication in new window or tab >>Philosophical controversies in the evaluation of medical treatments: With a focus on the evidential roles of randomization and mechanisms in Evidence-Based Medicine
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis examines philosophical controversies surrounding the evaluation of medical treatments, with a focus on the evidential roles of randomised trials and mechanisms in Evidence-Based Medicine. Current 'best practice' usually involves excluding non-randomised trial evidence from systematic reviews in cases where randomised trials are available for inclusion in the reviews. The first paper challenges this practice and evaluates whether adding of evidence from non-randomised trials might improve the quality and precision of some systematic reviews. The second paper compares the alleged methodological benefits of randomised trials over observational studies for investigating treatment benefits. It suggests that claims about the superiority of well-conducted randomised controlled trials over well-conducted observational studies are justified, especially when results from the two methods are contradictory. The third paper argues that postulating the unpredictability paradox in systematic reviews when no detectable empirical differences can be found requires further justification. The fourth paper examines the problem of absence causation in the context of explaining causal mechanisms and argues that a recent solution (Barros 2013) is incomplete and requires further justification. Solving the problem by describing absences as causes of 'mechanism failure' fails to take into account the effects of absences that lead to vacillating levels of mechanism functionality (i.e. differences in effectiveness or efficiency). The fifth paper criticises literature that has emphasised functioning versus 'broken' or 'non-functioning' mechanisms emphasising that many diseases result from increased or decreased mechanism function, rather than complete loss of function. Mechanistic explanations must account for differences in the effectiveness of performed functions, yet current philosophical mechanistic explanations do not achieve this. The last paper argues that the standard of evidence embodied in the ICE theory of technological function (i.e. testimonial evidence and evidence of mechanisms) is too permissive for evaluating whether the proposed functions of medical technologies have been adequately assessed and correctly ascribed. It argues that high-quality evidence from clinical studies is necessary to justify functional ascriptions to health care technologies.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2015. 20 p.
Theses in philosophy from the Royal Institute of Technology, ISSN 1650-8831
Evidence, randomized controlled trials, observational studies, systematic reviews, meta-analysis, methodology, process assessment, outcome assessment, medical care, randomization, evidence-based medicine, selection bias, philosophy of medicine, philosophy of science, mechanisms, quality of evidence, animal studies, treatment effect, causation by absence, medical technology
National Category
Health Care Service and Management, Health Policy and Services and Health Economy Philosophy Public Health, Global Health, Social Medicine and Epidemiology
Research subject
urn:nbn:se:kth:diva-161489 (URN)978-91-7595-489-9 (ISBN)
Public defence
2015-03-27, Kollegiesalen, Brinellvägen 8, KTH, Stockholm, 13:00 (English)

QC 20150312

Available from: 2015-03-12 Created: 2015-03-11 Last updated: 2015-03-12Bibliographically approved

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