Published on the Web 12/16/2007.
“What exactly are you inferring?” A closer look at hypothesis testing†
Article first published online: 9 DEC 2009
Copyright © 2008 SETAC
Environmental Toxicology and Chemistry
Volume 27, Issue 5, pages 1013–1019, May 2008
How to Cite
Newman, M. C. (2008), “What exactly are you inferring?” A closer look at hypothesis testing. Environmental Toxicology and Chemistry, 27: 1013–1019. doi: 10.1897/07-373.1
- Issue published online: 9 DEC 2009
- Article first published online: 9 DEC 2009
- Manuscript Accepted: 15 OCT 2007
- Manuscript Received: 19 JUN 2007
- Statistical significance;
- Experimental design;
- Confidence intervals;
This critical review describes the confused application of significance tests in environmental toxicology and chemistry that often produces incorrect inferences and indefensible regulatory decisions. Following a brief review of statistical testing theory, nine recommendations are put forward. The first is that confidence intervals be used instead of hypothesis tests whenever possible. The remaining recommendations are relevant if hypothesis tests are used. They are as follows: Define and justify Type I and II error rates a priori; set and justify an effect size a priori; do not confuse p(E | H0) and p(H0 | E); design tests permitting Positive Predictive Value estimation; publish negative results; estimate a priori, not post hoc, power; as warranted by study goals, favor null hypotheses that are not conventional nil hypotheses; and avoid definitive inferences from isolated tests.