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Re: st: RE: Re: fpower


From   Robert A Yaffee <bob.yaffee@nyu.edu>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: RE: Re: fpower
Date   Mon, 22 Jun 2009 05:48:17 -0400

Hi,
  Jack Cohen,  before he passed away, used F as his effect size index
for the Anova.   You can find this in Chapter 8 of his book on Power
Analysis for the Behavioral Sciences.   On page 284 of that 1988 book
he defines f = sqrt(eta^2/(1-eta^2)).  He considered a small effect size
that which had an f=0.10, a medium effect size, that which had an f=0.25,
and a large effect size that with an f=0.40.    He used these benchmarks
to help assess the power of an F test.
  Regards,
           Bob
  

Robert A. Yaffee, Ph.D.
Research Professor
Silver School of Social Work
New York University

NSF grant:
http://www.colorado.edu/ibs/es/nuclear_disaster_risk/principal_investigators.html
Biosketch: http://homepages.nyu.edu/~ray1/Biosketch2009.pdf

CV:  http://homepages.nyu.edu/~ray1/vita.pdf

----- Original Message -----
From: CHIDLOW Agnieszka <A.Chidlow@staffs.ac.uk>
Date: Sunday, June 21, 2009 8:25 pm
Subject: st: RE: Re: fpower
To: statalist@hsphsun2.harvard.edu


> Thank you!!
>  
> But is this based on your professional judgement, educated guess or a 
> literature I could refer to. I would like to learn this stuff myself.
>  
> Aggie
> 
> ________________________________
> 
> From: owner-statalist@hsphsun2.harvard.edu on behalf of Philip Ender
> Sent: Mon 22/06/2009 01:19
> To: statalist@hsphsun2.harvard.edu
> Subject: st: Re: fpower
> 
> 
> 
> Thank you very much for your e-mail and suggestions regarding fpower
> and anove (you are absolutely right, thanks for that).
> 
> If I can ask, why would you run "simpower nm year, reps(2000)" using 2000?
> 
> Once again, many thanks
> Aggie
> 
> ---------------------------------------------------------------
> 
> Aggie-
> 
> The minimum I would recommend is 1000 reps but since you have 8 groups
> I think 2000 would be better.
> 
> Best of luck.
> 
> --
> Phil Ender
> Statistical Consulting Group
> UCLA  Academic Technology Services
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