Which Test is Used to Verify Assumptions in TTest

*To*: mathgroup at smc.vnet.net*Subject*: [mg120132] Which Test is Used to Verify Assumptions in TTest*From*: Gregory Lypny <gregory.lypny at videotron.ca>*Date*: Sat, 9 Jul 2011 07:32:37 -0400 (EDT)

Hello everyone, I've run some simple t-tests of means using TTest and was pleased to see that Mathematica pretests for the validity of underlying assumptions. In a very skewed sample, I received a warning that the normality assumption had likely been violated. The warning looked like this: TTest::nortst: "At least one of the p-values in 0., resulting from a test for normality, is below 0.05. The tests in T require that the data is normally distributed. Is it possible to find out precisely which pretest Mathematica performed in order to generate that message? Regards, Gregory

**Follow-Ups**:**Re: Which Test is Used to Verify Assumptions in TTest***From:*Andy Ross <andyr@wolfram.com>

**Re: Which Test is Used to Verify Assumptions in TTest***From:*"Hobbs, Sylvia (DPH)" <sylvia.hobbs@state.ma.us>