In order to measure customer sentiment about mall decorations, Stephanie the stats intern developed a three-part coupon. She had staff members distribute these cards randomly through the mail at various times and locations. The recipient check how she or he felt about the decorations, used the coupon in a store, but then gave the other two parts to two friends, family, colleagues or acquaintances to use online in a similar way, generating two additionalleads each time. With this approach, there are only limited commonalities among the participants, just that they have met. The sample does grow somewhat exponentially. Which statistical sampling technique best describes her 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