[R] pairwise.t.test

[Thomas Chesney]

Thank you!
________________________________________
From: peter dalgaard [pdalgd at gmail.com]
Sent: Tuesday, February 10, 2015 12:05 PM
To: Thomas Chesney
Cc: r-help at r-project.org
Subject: Re: [R] pairwise.t.test

On 10 Feb 2015, at 11:45 , Thomas Chesney <Thomas.Chesney at nottingham.ac.uk> wrote:

> I'm using pairwise.t.test() with 6 groups, but the dataset the 6 groups are in actually contains 24 groups.
>
> When I run the test with all 24 groups the results I'm getting between Group 1 and Group 2 are very different from the results I'm getting between Group 1 and Group 2 when I split off the 6 groups and run the test. When only 6 groups are included the results are highly significant but with all 24 groups the results are insignificant.
>
> I'm not adjusting p.values. The code I'm running is:
>
> res <- pairwise.t.test(dat$Adopt, dat$Group, p.adj="none")
>
> I thought the above code would run exactly the same test on Groups 1 and 2, regardless of how many groups are in the dataset. Can anyone explain what's going on?

Check out pool.sd on the help page.

-pd


>
> Thank you,
>
> Thomas Chesney
>
>
>
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--
Peter Dalgaard, Professor,
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This message and any attachment are intended solely for the addressee
and may contain confidential information. If you have received this
message in error, please send it back to me, and immediately delete it. 

Please do not use, copy or disclose the information contained in this
message or in any attachment.  Any views or opinions expressed by the
author of this email do not necessarily reflect the views of the
University of Nottingham.

This message has been checked for viruses but the contents of an
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