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 <[email protected]>
Date: Sunday, June 21, 2009 8:25 pm
Subject: st: RE: Re: fpower
To: [email protected]
> 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: [email protected] on behalf of Philip Ender
> Sent: Mon 22/06/2009 01:19
> To: [email protected]
> 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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