Surveylogistic Question

[alanb4173]

Hi everyone-I have two different logistic models, call them Model A and Model B.  They are exactly the same, except Model B has some additional interactions added as predictors.  I would like to determine whether the additional predictors in Model B are significant as a whole.  Is there a way to do this in SAS?

[SteveDenham]

The best way to test as a whole would be to do a likelihood ratio test.  Since Model A is completely nested in Model B, the difference in the -2 log likelihoods should be asymptotically distributed as chi-squared with df=number of additional parameters.  ODS OUTPUT is your friend for getting the likelihoods into datasets where you can manipulate the values and do the calculations.  Oh, and I forgot this, everything between Model A and B has to really, really be exactly the same--no changes in PSUs or sampling weights.

Steve Denham