-------- Original Message --------
Subject: Re: p-values
Date: Fri, 28 Aug 2009 10:28:31 -0700 (PDT)
From: Samor Gandhi <[email protected]>
To: [email protected]
Thank you very much! What I meant with the sample size was about the
following:
If we have two group, in each group 10 sample (i.e. n=20), the t.test in
R can be used to get run the t-test (and/or Welch), and it gives the
t-value (t-statistic) and the theoretical p-value (from the t-
distribution)! What I am asking about is to get the t-value from the
t.test and run the test let say 100 times. What i wanted to know is
there an rule of thumb that tells how big n1 and n2 (n=n1+n2) should be
to run permutation for each time of these 100 times! So, would 8=10-2 be
good for each permutation! Because what I understand here (I am not a
mathematician) that one should compute first the t-value (i.e. using
t.test in R) and the compute 100 t-values due to permutation and then
see where does my first t-value lies and this would be the p-value! For
example if I have 4.332 as a t-value and this would be equal to the 8th
value in the permutations values (100 values), then my p-value would be
8/100=0.08! Is this correct?
Thank you in advance,
Samor
--- On *Fri, 8/28/09, morphmet /<[email protected]>/*
wrote:
From: morphmet <[email protected]>
Subject: Re: p-values
To: "morphmet" <[email protected]>
Date: Friday, August 28, 2009, 5:25 PM
-------- Original Message --------
Subject: Re: p-values
Date: Fri, 28 Aug 2009 04:55:24 -0700 (PDT)
From: Dennis E. Slice <[email protected]
</mc/[email protected]>>
To: [email protected]
</mc/[email protected]>
References: <[email protected]
</mc/[email protected]>>
Sokal and Rohlf. 1995. Biometry, 3rd ed.
Section 9.4 - t-test
Box 9.14 - Finding the sample size required and power for ANOVA
Rohlf and Sokal. 1995. Statistical Tables.
Table B - critical values for t
R Development Core Team (2005). R: A language and environment for
statistical computing. R Foundation for Statistical Computing, Vienna,
Austria. ISBN 3-900051-07-0, URL http://www.R-project.org.
Function: t.test()
-dslice
morphmet wrote:
>
>
> -------- Original Message --------
> Subject: p-values
> Date: Thu, 27 Aug 2009 15:22:48 -0700 (PDT)
> From: Samor Gandhi <[email protected]
</mc/[email protected]>>
> To: [email protected]
</mc/[email protected]>
>
>
>
> Dear all,
>
> What is the best way to compute the p-vallue from the t-statisic
> (t-value)? And how big the subsample should be?
>
> Many thanks,
> Samor
>
>
>
-- Dennis E. Slice
Associate Professor
Dept. of Scientific Computing
Florida State University
Dirac Science Library
Tallahassee, FL 32306-4120
-
Guest Professor
Department of Anthropology
University of Vienna
-
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