Mathematica 9 is now available
Services & Resources / Wolfram Forums / MathGroup Archive
-----

MathGroup Archive 2011

[Date Index] [Thread Index] [Author Index]

Search the Archive

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


  • Prev by Date: Re: Beeps in Mathematica
  • Next by Date: Re: derivative of matrix in mathematica
  • Previous by thread: Which Test is Used to Verify Assumptions in TTest
  • Next by thread: Re: Which Test is Used to Verify Assumptions in TTest