The positive approach to negative results in toxicology studies.

Negative results in toxicology studies are often as noteworthy as are results that detect significant toxicological effects. The results of 49.1% of all t tests published in Ecotoxicology and Environmental Safety in 1985 and 1986 were negative. However, despite the importance and prevalence of negative results in toxicology studies, they are frequently misinterpreted. Negative results from statistical tests that have poor statistical power can only be considered to be inconclusive. Because toxicology studies often use small sample sizes, such studies often have poor power to detect small, but biologically significant, effects. Toxicologists may improve the power of their tests by improving experiment design, increasing alpha, increasing sample size, or limiting the analysis to detection of large differences among samples. Selection of both sample size and alpha level should take considerations of statistical power into account.