Take a random percentage sample, in this example, 10%:

      sample 10

You can do this withing groups:

      by sex: sample 10

Take a random number sample, in this example, 100 records:

      sample 100, count

You can do this withing groups:

      by sex: sample 100, count

This version is also useful for picking the winner of a contest:

      sample 1, count

Take a sample of every nth record, in this example, keep every 10th record.:

      keep if mod(_n,10)==0