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MathGroup Archive 2006

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Re: t-test question

  • To: mathgroup at smc.vnet.net
  • Subject: [mg64167] Re: [mg64150] t-test question
  • From: Renan <renan.birck at gmail.com>
  • Date: Fri, 3 Feb 2006 01:03:54 -0500 (EST)
  • References: <200602030009.TAA10177@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Attila,
> 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...

I typed your data into Mathematica (5.2, Windows XP) and got:

In[1]:=
na=342
nb=170
Ua=6.39
Ub=6.07
xa=177.19
xb=170.37

Out[1] ... Out[6] ignored, because they're just what I typed in In[1].

In[7]:= Ue=(na-1)*Ua+(nb-1)Ub/na+nb-2

Out[7] := 2349.99

In[8] := t0 = Abs[xa - xb]/Sqrt[Ue*(1/na+1/nb)]

Out[8] := 1.49918

I don't know how to interpret this result, so I will leave just the
answers here.


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