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F-test = t-test squared - how to show? (beginner question)
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Zootal  
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 More options Oct 28, 3:18 pm
Newsgroups: sci.stat.math
From: "Zootal" <use...@spam.zootal.nospam.com>
Date: Tue, 27 Oct 2009 21:18:32 -0700
Local: Wed, Oct 28 2009 3:18 pm
Subject: F-test = t-test squared - how to show? (beginner question)
I hope this is the appropriate place to post this question. I am attempting
to show that an F-statistic is equal to a t-statistic squared, or IOW F =
t^2. I am working with linear regression and extra sum of squares tests. How
would one go about showing this? Or, can some kind soul nudge me in the
right direction?

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Jack Tomsky  
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 More options Oct 29, 6:28 am
Newsgroups: sci.stat.math
From: Jack Tomsky <jtom...@ix.netcom.com>
Date: Wed, 28 Oct 2009 15:28:11 EDT
Local: Thurs, Oct 29 2009 6:28 am
Subject: Re: F-test = t-test squared - how to show? (beginner question)

> I hope this is the appropriate place to post this
> question. I am attempting
> to show that an F-statistic is equal to a t-statistic
> squared, or IOW F =
> t^2. I am working with linear regression and extra
> sum of squares tests. How
> would one go about showing this? Or, can some kind
> soul nudge me in the
> right direction?

The easiest way is to work with the canonical forms.

F(m,n) = [X2(m)/m]/[X2(n)/n],

where F(m,n) is an F with m and n degrees of freedom, X2(m) is a chi-square with m degrees of freedom, X2(n) is a chi-square with n degrees of freedom, and X2(m) and X2(n) are independent.

In particular, for m = 1,

F(1,n) = X2(1)/[X2(n)/n] = = z^2/[X2(n)/n] =
[z/sqrt(X2(n)/n)]^2 = [t(n)]^2,

where z ~ N(0,1) and t(n) is Student's t with n degrees of freedom.

Thus an F with 1 and n degrees of freedom is the square of a t with n degrees of freedom.

Jack
www.tomskystatistics.com


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Adole  
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 More options Nov 8, 8:19 am
Newsgroups: sci.stat.math
From: Adole <dst191...@gmail.com>
Date: Sat, 7 Nov 2009 13:19:24 -0800 (PST)
Local: Sun, Nov 8 2009 8:19 am
Subject: Re: F-test = t-test squared - how to show? (beginner question)
On Oct 28, 1:28 pm, Jack Tomsky <jtom...@ix.netcom.com> wrote:

The reason this is not a great explanation is because you don't
explain (or show) how X2 and Z2 are approximated to be the same.
Therefore, this equations carries assumptions which from the student's
perspective aren't demonstrated to be valid.

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