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Some consequences using pooled samples versus individual samples and pooled samples with various relation between sampling error and uncertainty due to chemical analysis
Executive, Naturhistoriska riksmuseet, NRM.
Responsible organisation
2008 (English)Report (Other academic)
Abstract [sv]

Choosing an appropriate sampling strategy for environmental monitoring or storingsamples in Environmental Specimen Banks for future analyses includes the importantdecision of using individual or pooled samples. A number of advantages usingindividual samples for temporal trend studies can be identified e.g. that informationabout sample variance is important in it self and changes in variance is often the firstsign of a change in contaminant burden, freedom of choosing an appropriate centralmeasure (for right skewed distributions i.e. geometric mean values or medians)whereas pooled samples will represent arithmetic means. Furthermore, individualsampling enables adjustments for confounding factors (e.g. fat content, age, size) anddetection of extreme values. However, resources may be saved by using pooledsamples, if the sample variance is dominated by small-scale differences in time orspace or by genetic and/or physiological differences among individual biologicalsamples rather than of instrumental errors at the chemical analyses. The statisticalpower at temporal or spatial studies is determined by the random/unexplained samplevariation. The relation between the instrumental error and other sources of variation aswell as the relation between the cost for chemical analysis and collection andpreparation of samples will determine the number of individual samples in each pooland the number of pools that should be analysed to achieve high cost efficiency.Various scenarios of different number of individual samples, different number ofpooled samples containing various number of individual specimens, different relationbetween instrumental error and other sources of sample variance have been comparedby simulating random sampling from computer generated populations using realisticmeasures of variation from ongoing monitoring activities. The results may giveguidance to the selection of a cost efficient sampling strategy

Place, publisher, year, edition, pages
Naturhistoriska riksmuseet, enheten för miljögiftsforskning , 2008.
Keyword [en]
biota, oceans, environment
Keyword [sv]
kemisk analys, provtagning, miljöövervakning, strategi, provbankning, Marin miljö, analysfel, individuella prover, Poolad prover
National Category
Environmental Sciences
Research subject
Miljöövervakningens programområden, Coast and sea; Environmental Objectives, A Balanced Marine Environ­ment, Flourishing Coastal Areas and Archipelagos
URN: urn:nbn:se:naturvardsverket:diva-403Local ID: B02B2734-C296-499D-8269-DC70CB219EF0OAI: diva2:657968
Available from: 2013-10-21 Created: 2013-10-21 Last updated: 2013-12-11Bibliographically approved

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