Exploring Equivalence Testing with the Updated TOSTER R Package

Abstract

Despite decades of methodological guidance, researchers continue to misinterpret non-significant results as evidence for the absence of an effect. Equivalence testing via two one-sided tests (TOST) provides a principled alternative, but adoption remains limited by software accessibility and lack of training. The TOSTER R package, originally developed by Lakens (2017), made TOST accessible to experimental psychologists. This paper describes a major update to the package that expands its scope with (1) a unified t-test interface supporting both equivalence and minimal effect testing, (2) a simplified hypothesis testing interface returning standard R objects, (3) tools for computing and testing standardized effect sizes and correlations, (4) robust and resampling-based alternatives including bootstrap and permutation tests, (5) equivalence testing for ANOVAs, and (6) power analysis and sample size planning. Each capability is demonstrated with worked examples. TOSTER is also available as a jamovi module for researchers who prefer a graphical interface.