       Re: t-test question

• To: mathgroup at smc.vnet.net
• Subject: [mg64186] Re: [mg64150] t-test question
• From: Darren Glosemeyer <darreng at wolfram.com>
• Date: Sat, 4 Feb 2006 04:13:41 -0500 (EST)
• Sender: owner-wri-mathgroup at wolfram.com

```As an aside to the responses that have already been posted, if you have the
data at hand, you can use MeanDifferenceTest to perform the test directly
from the data.

In:= << Statistics`HypothesisTests`

In:= data1 = Table[Random[], {20}];

In:= data2 = Table[Random[Real, {.3, 1.3}], {35}];

This will give the signed t-statistic for a difference of 0, which is the
difference in the case you described, and the p-value for the two-sided test.

In:= MeanDifferenceTest[data1, data2, 0, TwoSided -> True, FullReport ->
True]

Out= {FullReport ->    MeanDiff    TestStat   Distribution                ,
-0.265388   -3.22715   StudentTDistribution[41.354]

>    TwoSidedPValue -> 0.00244793}

The two-sided p-value is the p-value for the absolute value of the
t-statistic, which is the case you described.

Darren Glosemeyer
Wolfram Research

At 07:09 PM 2/2/2006 -0500, Csukas Attila wrote:
>Dear all,
>
>I have found an equation for comparing two means.
>
>Ue = (na - 1)*Ua + (nb - 1)Ub/na + nb - 2    This is for the pooled
>value of distribution and
>
>t0 = |xa-xb|/ Root Ue*(1/na+1/nb)   This is for the t value.
>
>Sample values
>na=342
>nb=170
>Ua=6.39
>Ub=6.07
>xa=177.19
>xb=170.37
>
>Does anybody have idea how this works in Mathematica?
>I am not familiar with Mathematica syntax but interested how would this
>work...
>
>Any help and idea appreciated.
>
>Attila

```

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