This is what SAS's senior statistician said.

Russell,

As noted in replies to your post in the Statistical Procedures Community, the model with DIST=BIN and LINK=IDENTITY is considered a linear probability model. The model without DIST=BIN assumes a normal response and the normal log likelihood is then maximized. The mean of the binomial is a probability, while the mean of a normal is not, so I don't see how the model without DIST=BIN could be called a linear probability model.

PROC GENMOD models the probability of the lowest response level by default. You should explicitly specify the level you want to model by specifying that level in the EVENT= option following the response variable. If you have a binary predictor variable with values 0 or 1, it is best to not specify it in the CLASS statement since, by default, that will cause the estimated parameter for that variable to correspond to the lowest level, 0, rather than 1. If you do specify it in the CLASS statement, use the REF= option following the variable to specify that level 0 is the reference level. For example,

proc genmod;

class x(ref="0");

model response(event="1")=x / dist=binomial;

run;

---

David Schlotzhauer

Senior Statistician

SAS Institute Inc.

phone: 919.677.8008

toll free: 800.727.0025

web: http://support.sas.com/ts