# st: re: indirect effects in logit model

 From Kit Baum To statalist@hsphsun2.harvard.edu Subject st: re: indirect effects in logit model Date Mon, 28 May 2007 17:24:13 -0400

Charlie said

My model is compounded. That is,
Y=X1+X2+X3 (Y= binary dependent variable with very rare case of "1")
but, one independent variable of the equation (X2, continuous
variables) is a function of X1; X2=X1+ X4

As you see in the above, the major independent variable is X1.
X1 has a direct effect on Y and also an indirect effect via X2 on Y.

I want to estimate X1's direct and indirect effects via on Y.

If X2 is a deterministic function of X1, then just substitute its equation into the main equation, and estimate
logit y x1 x4 x3

If the original logit is I = b0 + b1 x1 + x2 x2 + b3 x3 + error, then you are now estimating
I = b0 + (b1+b2) x1 + b2 x4 + b3 x3 + error

and you can calculate the direct effect of x1 as its estimated coefficient minus b2-hat, using lincom.

Kit Baum, Boston College Economics and DIW Berlin
http://ideas.repec.org/e/pba1.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/support/faqs/res/findit.html
* http://www.stata.com/support/statalist/faq
* http://www.ats.ucla.edu/stat/stata/