In order to measure patron reactionsto potential promotional coupon programs among the mall's most loyal customers, Steven the stats intern was assigned to collect some data. He emailed a selection of the most frequent customers as identified by the managers of a number of boutique shops and smaller stores in the mall. These managers are experts on their regular customers.

Which statistical sampling technique best describes his methodology?

1. cluster sampling
2. convenience sampling
3. judgment sampling
4. network sampling
5. quota sampling
6. simple random sample
7. snowball sampling
8. stratified sampling
9. systematic sampling