For the following four exercises, determine the type of sampling used (simple random, stratified, systematic, cluster, or convenience). 12. A group of test subjects is divided into twelve groups; then four of the groups are chosen at random. 13. A market researcher polls every tenth person who walks into a store. 14. The first 50 people who walk into a sporting event are polled on their television preferences. 15. A computer generates 100 random numbers, and 100 people whose names correspond with the numbers on the list are chosen.