Programming the statistical procedures from SAS

PROC LOGISTIC PEVENT= option, priors for individual strata?

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Occasional Contributor
Posts: 10

PROC LOGISTIC PEVENT= option, priors for individual strata?

Hi!  In PROC LOGISTIC one can specify a prior distribution of outcomes using the PEVENT= option on the MODEL statement.  So, if the training sample has equal number of events and non-events, but the true proportion of events in the population is 5%, just set PEVENT = 0.05 to adjust for the bias in the sample.

 

Now, suppose life is a bit more complicated.  Let there be a variable called subgroup with values "A" and "B."  Perhaps my training sample is split into 20% "A" and 80% "B" but the true population is 5% "A" and 95% "B," and further suppose that the sample has 30% events in subgroup = "A" and 40% events in subgroup = "B," although the "A" population really has 2% events, and the "B" population really has 6% events.  Is there a way to use the PEVENT= option (and perhaps this requires another option, too) to adjust the results to the population proportions?

 

Thanks!

Occasional Contributor
Posts: 10

Re: PROC LOGISTIC PEVENT= option, priors for individual strata?

I believe that adding a WEIGHT variable can take care of the relative percentages of "A" and "B," but that still leaves me wondering how (and whether) PEVENT and / or other options can properly adjust the percentages of events within each category.
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