Re: Which Test is Used to Verify Assumptions in TTest

*To*: mathgroup at smc.vnet.net*Subject*: [mg120163] Re: Which Test is Used to Verify Assumptions in TTest*From*: "Hobbs, Sylvia (DPH)" <sylvia.hobbs at state.ma.us>*Date*: Sun, 10 Jul 2011 05:03:09 -0400 (EDT)*References*: <201107091132.HAA13524@smc.vnet.net>

In the documents, look under built in diagnostic testing. Sylvia Hobbs ________________________________________ From: Gregory Lypny [gregory.lypny at videotron.ca] Sent: Saturday, July 09, 2011 7:32 AM To: mathgroup at smc.vnet.net Subject: [mg120163] Which Test is Used to Verify Assumptions in TTest 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

**References**:**Which Test is Used to Verify Assumptions in TTest***From:*Gregory Lypny <gregory.lypny@videotron.ca>