Date: Wed, 24 Feb 2010 11:53:38 +0100
Reply-To: Antonio ML <firstname.lastname@example.org>
Sender: "SPSSX(r) Discussion" <SPSSX-L@LISTSERV.UGA.EDU>
From: Antonio ML <email@example.com>
Subject: Re: power for a Mixed design (one random and one fixed)
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Thank you Bruce.
I wonder if there any web site of macro that can perform those
calculation form me.. when I know the levels and sizes
And you're rigth I can omit 'pat' from 'medida By pat trat'
Bruce Weaver escribiˇ:
> amllistas wrote:
>> Hello List.
>> Now I'm wondering how to compute the POWER of a mixed model test....
>> The think is how to evaluate how good is it or if a would need to sample
>> more (ufff!!!! very expensive and tedious, but if with 4 o 5 more i
>> increase the power a lot i can consider it).
>> Thank you all in advance.
>> Finally , my syntax looks is like this:
>> medida BY pat trat
>> /CRITERIA = CIN(95) MXITER(100) MXSTEP(5) SCORING(1)
>> SINGULAR(0.000000000001) HCONVERGE(0, ABSOLUTE) LCONVERGE(0, ABSOLUTE)
>> PCONVERGE(0.000001, ABSOLUTE)
>> /FIXED = trat | SSTYPE(3)
>> /METHOD = REML
>> /PRINT = SOLUTION TESTCOV
>> /RANDOM INTERCEPT trat | SUBJECT(pat) COVTYPE(VC)
>> /EMMEANS = TABLES(trat) COMPARE ADJ(BONFERRONI) .
>> and my data like this (tab separated, and a dot as decimal):
>> trat pat medida
>> 1 1 4
>> 1 2 10
>> --- snip ---
> If you are asking how to compute post-hoc power, I would advise you not to
> bother, as post-hoc power is just a transformation of the p-value. I.e., if
> p < .05, you will find that post-hoc power was adequate, and if p > .05,
> you'll find it was inadequate.
> If you are asking how to compute an a priori sample size estimate for a
> multilevel (linear) regression model, take a look at Chapter 8 in Jos
> Twisk's book, Applied Multilevel Analysis. It boils down to computing a
> standard sample size estimate, and then applying a "correction factor",
> which takes into account the multilevel nature of the data. However, there
> are two possible correction factors. Twisk describes one as "liberal", and
> the other as "conservative". He discusses the relative merits of the two,
> and the situations in which they might be appropriate. He concludes:
> "In practice, the 'conservative' sample size procedure is mostly used.
> However, most researchers do not reealise that this procedure leads to an
> overestimation of the required sample size when the randomisation is
> performed on the patient level." (Twisk 2006, pp. 130-131)
> p.s. - In your MIXED syntax, I believe you can omit "pat" from "medida BY
> pat trat".
> Bruce Weaver
> "When all else fails, RTFM."
> NOTE: My Hotmail account is not monitored regularly.
> To send me an e-mail, please use the address shown above.
> View this message in context: http://old.nabble.com/2-ways-MANOVA--or-what--and-how...-tp26791541p27652620.html
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Gracias, Efharisto poli, Grazie, Thank you, Tak,
Shukran, Hvala, Blagodaria, Bedankt, Danke sch÷n,
Shukriya, Tesekuler, Merci, Spasiba, Obrigato,
Go raibh maith agat, Arigato, Dishklenle,
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