Enhancing the interpretation of statistical P values in toxicology studies: implementation of linear mixed models (LMMs) and standardized effect sizes (SESs).
In this paper, we compare the traditional ANOVA approach to analysing data from 90-day toxicity studies with a more modern LMM approach, and we investigate the use of standardized effect sizes. The LMM approach is used to analyse weight or feed consumption data. When compared to the week-by-week ANOVA with multiple test results per week, this approach results in only one statement on differences in weight development between groups. Standardized effect sizes are calculated for the endpoints: weight, relative organ weights, haematology and clinical biochemistry. The endpoints are standardized, allowing different endpoints of the same study to be compared and providing an overall picture of group differences at a glance. Furthermore, in terms of standardized effect sizes, statistical significance and biological relevance are displayed simultaneously in a graph.
BioMath GmbH, Schnickmannstr. 4, 18055, Rostock, Germany. kerstin.schmidt@biomath.de.
Kerstin
K
Schmidt
BioMath GmbH, Schnickmannstr. 4, 18055, Rostock, Germany.
Jörg
J
Schmidtke
Institute for Biosafety in Plant Biotechnology, Julius Kühn-Institut, Federal Research Centre for Cultivated Plants, Erwin-Baur-Str. 27, 06484, Quedlinburg, Germany.
Christian
C
Kohl
Institute for Biosafety in Plant Biotechnology, Julius Kühn-Institut, Federal Research Centre for Cultivated Plants, Erwin-Baur-Str. 27, 06484, Quedlinburg, Germany.
Ralf
R
Wilhelm
Institute for Biosafety in Plant Biotechnology, Julius Kühn-Institut, Federal Research Centre for Cultivated Plants, Erwin-Baur-Str. 27, 06484, Quedlinburg, Germany.
Joachim
J
Schiemann
Biometris, Wageningen UR, P.O. Box 16, 6700 AA, Wageningen, The Netherlands.
Hilko
H
van der Voet
Institute for Food Toxicology and Analytical Chemistry, University of Veterinary Medicine Hannover, Bischofsholer Damm 15, 30173, Hannover, Germany.
Pablo
P
Steinberg
D000704:Analysis of Variance; D000818:Animals; D001835:Body Weight; D016014:Linear Models; D008297:Male; D009929:Organ Size; D030821:Plants, Genetically Modified; D051381:Rats; D018675:Toxicity Tests / Q000379:methods* / Q000592:standards* / Q000706:statistics & numerical data; D014116:Toxicology / Q000592:standards / Q000706:statistics & numerical data*; D003313:Zea mays
90-day toxicity study; ANOVA; Linear mixed models; P values; Repeated measurements; Standardized effect sizes