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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>