After deciding on the research approach and instruments, the marketing researcher must design a sampling plan. A firm can rarely take a census of all possible users of a new product nor can they all be interviewed. Therefore, a firm must select a sample of the group to be interviewed. A sample is a subset from a larger population. 

Which sampling approaches are used in the following cases? 

a) Suppose, a researcher at Lauder Business School divides incoming students into mutually exclusive groups (such as cohorts IBA2024, IML2024, SFBA 2024), and draws a sample of the groups to interview.

b) Imagine, a researcher at Lauder Business School is equipped with a list of all incoming students. He generates a random number (i.e., 5) and thus, selects every 5th student as a prospect for his study.