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st: st: Biprobit for Endogenous Binary Regressor-Opposite Sign Interpretation?
From
"Clifton Chow" <[email protected]>
To
[email protected]
Subject
st: st: Biprobit for Endogenous Binary Regressor-Opposite Sign Interpretation?
Date
Thu, 14 Jun 2012 00:20:57 -0500
I am wondering if anyone has run a biprobit to correct for an endogenous binary regressor and got an opposite sign from the same regressor in an ordinary probit? My main equation is a probit predicting Work(LFP). However, one of my regressors, a policy instrument that is binary, is endogenous, so I ran a biprobit with 2 instruments (Ivprobit is not advisable when the endogenous regressor is binary). As you can see below, the coefficient on XBinEndog is negative, but if I treated it as an exogenous binary variable in an ordinary probit, it is positive as hypothesized. I am concerned as the Wald test on rho is significant and not sure how the switch in sign can be interpreted.
Any suggestions would be great. I have checked the archives on biprobit, and I can't find any similar posting.
Thanks
Main Probit Eq.
Work |
X1 | -.3708311 .1433871 -2.59 0.010 -.6518647 -.0897974
X2 | -.174675 .1370149 -1.27 0.202 -.4432192 .0938692
X3 | -2653913 .1184114 -2.24 0.025 -.4974733 -.0333093
XBinEndg | -.8087503 .3468027 -2.33 0.020 -1.488471 -.1290294
-----------------------------------------------------------------------------------------------------------------
XBinEndg |
Z1 | 1.204996 .2139061 5.63 0.000 .7857481 1.624245
Z2 | .6297623 .1320375 4.77 0.000 .3709736 .8885509
_cons | -1.171011 .0843702 -13.88 0.000 -1.336374 -1.005649
-------------+----------------------------------------------------------------
/athrho | .5757204 .2832209 2.03 0.042 .0206177 1.130823
-------------+----------------------------------------------------------------
rho | .519548 .206771 .0206148 .8113008
------------------------------------------------------------------------------
Wald test of rho=0: chi2(1) = 4.13212 Prob > chi2 = 0.0421
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