MBESS is an R package that was developed primarily to implement important but nonstandard methods for the behavioral, educational, and social sciences. The generality and applicability of many of the functions contained in MBESS have allowed the package to be used in a variety of other disciplines. Both MBESS and R are open source and freely available from The R Project's Comprehensive R Archive Network. The MBESS Web page contains the reference manual, source code files, and binaries files. MBESS (and R) is available for Apple Macintosh, Microsoft Windows, and Unix/Linux operating systems.

The major categories of functions contained in MBESS are (a) estimation of effect sizes (standardized and unstandardized), (b) confidence interval formation based on central and noncentral distributions (t, F, and χ2), (c) sample ...