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Re: st: Computing semipartial correlations


From   Richard Williams <Richard.A.Williams.5@nd.edu>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Computing semipartial correlations
Date   Tue, 16 Dec 2003 18:39:54 -0500

At 11:54 AM 12/11/2003 -0500, Richard Williams wrote:
The pcorr routine uses the following formula to compute partial correlations:

t/sqrt(t^2 + N - K -1) where N = Sample size and K = # of X variables

This is not the most intuitive formula in the world, but it works! I would like to modify the program to compute semipartial correlations.
To follow up on my own message: ssc now has a routine I have written called -pcorr2- (type -findit pcorr2- to get it). It works exactly like Stata's -pcorr- command, except it reports both the partial and semipartial correlations (-pcorr-- only reports the partials). -pcorr- uses a wildly non-intuitive but correct formula to get the partials so the only real trick was figuring out the corresponding wildly non-intuitive but correct formula for the semipartials. Thanks to Nick Cox for telling me how to make this publicly available and to Kit Baum for adding it to ssc.


-------------------------------------------
Richard Williams, Associate Professor
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EMAIL: Richard.A.Williams.5@ND.Edu
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