The unequal variance t-test is an underused alternative to Student's t-test and the Mann–Whitney U test

TLDR

Statistical comparisons of group means or medians are routine in behavioral ecology and other sciences, yet the unequal‑variance t‑test is frequently neglected because many researchers are unaware of its advantages over the standard Student’s t‑test. The article advocates for broader use of the unequal‑variance t‑test. The author distinguishes the two t‑tests by noting that their degrees‑of‑freedom calculations differ, allowing confident identification of each test in published studies. In a survey of 130 papers, only 9 instances (4 papers) used the unequal‑variance t‑test, compared with 67 uses of Student’s t‑test and 43 uses of Mann–Whitney U.

Abstract

Often in the study of behavioral ecology, and more widely in science, we require to statistically test whether the central tendencies (mean or median) of 2 groups are different from each other on the basis of samples of the 2 groups. In surveying recent issues of Behavioral Ecology (Volume 16, issues 1–5), I found that, of the 130 papers, 33 (25%) used at least one statistical comparison of this sort. Three different tests were used to make this comparison: Student’s t-test (67 occasions; 26 papers), Mann–Whitney U test (43 occasions; 21 papers), and the t-test for unequal variances (9 occasions; 4 papers). My aim in this forum article is to argue for the greater use of the last of these tests. The numbers just related suggest that this test is not commonly used. In my survey, I was able to identify tests described simply as ‘‘t-tests’’ with confidence as either a Student’s t-test or an unequal variance t-test because the calculation of degrees of freedom from the 2 sample sizes is different for the 2 tests (see below). Hence, the neglect of the unequal variance t-test illustrated above is a real phenomenon and can be explained in several (nonexclusive ways) ways: 1. Authors are unaware that Student’s t-test is unreliable