Having your test list order represent a random sample of the entire list is critical to ensuring that your test results will be repeatable.  After all, that’s one of the primary reasons direct mail is so powerful! Taking an “nth select” is a selection technique for a list test mailing where the list owner selects names based on the size of a test sample in relation to the size of the list.  For example, if your list segment has a total of 100,000 names available and you only want to test 7,500 records from that list selecting an nth will ensure that the 7,500 records are pulled without prejudice to a recency, geography, etc beyond what was stated in the universe segment.