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Merging precaution with sound science under the Endangered Species Act


Hypothesis tests, which aim to minimize type I errors (false positive results), are standard procedures in scientific research, but they are often inappropriate in Endangered Species Act (ESA) reviews, where the primary objective is to prevent type II errors (false negative results). Recognizing this disparity is particularly important when the best data available are sparse and therefore lack statistical power, because hypothesis tests that use data sets with low statistical power are likely to commit type II errors, thereby denying necessary protection to threatened and endangered species. Equivalence tests can alleviate this problem, and ensure that imperiled species receive the benefit of the doubt, by switching the null and alternative hypotheses. These points are illustrated by critiquing a recent review of ESA requirements for endangered fishes in Upper Klamath Lake (southern Oregon).