Rich -
You might want to consider doing some Resampling (Cross-Validation,
Bootstrap)
as you continue through your analyses.
-- Joe
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Joe Ward____________________________ Health Careers High School
167 East Arrowhead Dr _________________ 4646 Hamilton Wolfe
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Phone: 210-433-6575__________________ Phone: 210-617-5400
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http://www.ijoa.org/joeward/wardindex.html
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----- Original Message -----
From: <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Friday, December 08, 2000 3:30 PM
Subject: Statistical penalties for sequential analyses
> Need some advice. We are doing a series of tests looking for correlations
> among age-sensitive variables in a population of mice. We will have about
> 600 mice in all, and it will take 3 years to test each mouse at about 200
> mice tested each year.
>
> We are considering three strategies:
>
> A) Wait 3 years until all the data are in; then do the analyses.
>
> B) Analyze the data on the first 300 mice, and publish anything that looks
> exciting and meets conventional significance criteria. When the second set
> of mice is finished, we can use these second 300 animals as a replicate
> samples to (try to) confirm the significant findings we reported on the
first
> set. And we can also pool all 600 mice to obtain higher statistical power
> than we had for the initial analysis with N = 300.
>
> Of course this represents testing some hypotheses twice, and thus
increases
> the Type I error rate. I suspect that there are theoretically justified
> methods for adjusting significance criteria to "adjust" for taking two
looks
> at the data, but I don't know how to do this. Anyone have a recipe, or a
> reference to get me started?
>
> Thanks.
>
> Rich Miller
> University of Michigan
>
> Reply to: [EMAIL PROTECTED]
>
>
> Sent via Deja.com http://www.deja.com/
> Before you buy.
>
>
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