How to quantify support for and against the null hypothesis: A flexible WinBUGS implementation of a default Bayesian t test

We propose a sampling-based Bayesian t test that allows researchers to quantify the statistical evidence infavor of the null hypothesis. This Savage-Dickey (SD) t test is inspired by the Jeffreys-Zellner-Siow (JZS) t test recently proposed by Rouder Speckman, Sun, Morey, and Iverson (2009). The SD test retains the key concepts of the JZS test but is applicable to a. wider range of statistical problems. The SD test allows researchers to test order restrictions and applies to two-sample situations in which the different groups do not share the same variance.