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Re: st: Computing semipartial correlations

From   Richard Williams <>
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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