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Re: st: p value precision


From   Thomas Trikalinos (.Mac) <ttrikalin@mac.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: p value precision
Date   Mon, 17 May 2004 17:13:13 +0300

Hi James:
None of the available meta commands can give you what you want straightforwardly. (as far as I know)

1. metap synthesizes p-values. Do you perform a p-value synthesis?

2. For the cumulative meta-analysis, you can always compute the p-values yourself, with little effort.
It may differ depending on the effect size you are synthesizing.
The quotient Summary_effect_size / SE(Summary_effect_size) is a Z statistic ~N(0, 1). So you can calculate the p-value of Z by yourself for every step of the cumulative meta-analysis and then convert Z1, Z2,..., Zi to P-val1, Pval2, Pvali using something like

. gen PValue = 2*(1-norm(abs(Z_variable))), with as much precision as you want.

I don't know what you want these values for, though.

Tom

NB: The Summary_effect_size must be normally distributed, so use log(OR) or log(RR) instead of OR, RR. RD's, d's, Fischer transformed r's etc are used as is.


On May 17, 2004, at 16:40, Cook, James R MD wrote:


I am attempting a cumulative meta-analysis of 11 studies and after fourth study (by date) the p-value is 0.0000 and remains so thereafter. Does anyone know of a program that will allow more than 4 digits of precision for the p-value?
Will -metap- help? It seems to have 6 digits in the results.


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