hello,
my data include two variables with 20,000 records. One is whether or not received a product sample and the other is whether use the product or other products after received the product sample. I wanted to calculate the odds ratio to conclude that the consumer who received the product sample would be 2 times likely to use the product than the consumer who didn't receive the sample. However the product has only 3% of market share among all the products consumers use.
how to solve the problem in SAS?
I'm very appreciative of any helps?
Ethan
Here's a good quick reference, Paul Allisons thoughts on the issue
http://statisticalhorizons.com/logistic-regression-for-rare-events
You can google with the following term to get more responses : Logistic regression rare events
Exact Logistic Regression
Since you describe a 2x2 table, you could avoid fitting a model altogether and simply use PROC FREQ and request an exact estimate of the odds ratio with the EXACT OR; statement.
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