Making the right conclusions based on wrong results and small sample sizes: interpretation of statistical tests in ecotoxicology

Ecotoxicology and Environmental Safety
Magnus Wang, Michael Riffel

Abstract

In environmental risk assessments statistical tests are a standard tool to evaluate the significance of effects by pesticides. While it has rarely been assessed how likely it is to detect effects given a specific sample size, it was never analysed how reliable results are if the test preconditions, particularly of parametric tests, are not fulfilled or how likely it is to detect deviations from these preconditions. Therefore, we analyse the performance of a parametric and a non-parametric test using Monte Carlo simulation, focussing on typical data used in ecotoxicological risk assessments. We show that none of the data distributions are normal and that for typical sample sizes of N<20 it is very unlikely to detect deviations from normality. Non-parametric tests performed markedly better than parametric tests, except when data were in fact normally distributed. We finally discuss the impact of using different tests on pesticide risk assessments.

References

May 1, 1992·Neurotoxicology and Teratology·K E Muller, V A Benignus
Jun 1, 2002·Environmental Science & Technology·Arnd WeyersHans T Ratte
Oct 17, 2009·Environmental Biosafety Research·Joe N PerryHilko van der Voet

Citations

Feb 14, 2012·Ecotoxicology and Environmental Safety·Kerry BrinkRiana Bornman
Jan 1, 2014·Environmental Toxicology and Chemistry·Mira Kattwinkel, Matthias Liess
Mar 29, 2016·Integrated Environmental Assessment and Management·Eduard Szöcs, Ralf B Schäfer
May 9, 2015·Environmental Science and Pollution Research International·Eduard Szöcs, Ralf B Schäfer
Sep 19, 2012·Environmental Toxicology and Pharmacology·Kerry BrinkRiana Bornman
Apr 25, 2015·Environmental Science and Pollution Research International·Paula Suares-RochaMaria Aparecida Marin-Morales
Dec 29, 2020·PeerJ·Signe M JensenChristian Ritz

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