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From | Christopher Baum <kit.baum@bc.edu> |
To | "statalist@hsphsun2.harvard.edu" <statalist@hsphsun2.harvard.edu> |
Subject | Re: Re: st: comparing coefficients using suest (same sample, same DV) |
Date | Tue, 14 Aug 2012 14:16:33 +0000 |
<> On Aug 14, 2012, at 2:33 AM, Tirthankar wrote: > sysuse auto, clear > gmm (price - {xb: mpg foreign}-{b0}) /// regression 1 > (price - {xc: mpg foreign rep78}-{c0}), /// regression 2 > winitial(identity) /// > instruments(1: mpg foreign) /// regressors exogenous > instruments(2: mpg foreign rep78) /// > wmatrix(unadjusted, independent) /// moment conditions independent > > // test > test [xb_mpg]_cons = [xc_mpg]_cons This is indeed a more elegant way to do this, but note that it gets a bit messed up a bit because of the missing cases in rep78 that affect the second model but not the first. If applied to my prior example, sysuse auto, clear gmm (price - {xb: mpg}-{b0}) /// regression 1 (price - {xc: mpg trunk}-{c0}), /// regression 2 winitial(identity) /// instruments(1: mpg) /// regressors exogenous instruments(2: mpg trunk) /// wmatrix(unadjusted, independent) /// moment conditions independent // test test [xb_mpg]_cons = [xc_mpg]_cons It yields roughly the same p-value as does my earlier posting, keeping in mind that GMM uses z-statistics rather than t-statistics. Kit Kit Baum | Boston College Economics & DIW Berlin | http://ideas.repec.org/e/pba1.html An Introduction to Stata Programming | http://www.stata-press.com/books/isp.html An Introduction to Modern Econometrics Using Stata | http://www.stata-press.com/books/imeus.html * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/