Controlling the false discovery rate and increasing statistical power in ecological studies

Abstract

Ecologists routinely use Bonferroni-based methods to control the alpha inflation associated with multiple hypothesis testing, despite the aggravating loss of power incurred. Some critics call for abandonment of this approach of controlling the familywise error rate (FWER), contending that too many unwary researchers have adopted it in the name of scientific rigour even though it often does more harm than good. We do not recommend rejecting multiplicity correction altogether. Instead, we recommend using an alternative approach. In particular, we advocate the Benjamini–Hochberg and related methods for controlling the false discovery rate (FDR). Unlike the FWER approach, which safeguards against falsely rejecting even a single null hypothesis, the FDR approach controls the rate at which null hypotheses are falsely rejected (i.e., false discoveries are made). The FDR approach represents a compromise between outright refusal to control for multiplicity, which maximizes alpha inflation, and strict adherence to FWER control, which minimizes power. We review the multiplicity problem, illustrate the advantage of the FDR approach, and promote this approach for widespread adoption in ecology.