For the following two cases, determine which sampling plan was used.

Case 1: In an opinion poll, an airline company made a list of all its flights and then selected a simple random sample of 30 flights. All the passengers on those flights selected were asked to fill out a questionnaire form.

Case 2: A departmental store wanted to find out if customers would be willing to pay slightly higher prices for their products in order to have a smartphone app that customers can use to help them locate items in the store. The store hired an interviewer John and placed him at the only entrance on a particular day. John was tasked to collect a sample of 100 opinions by interviewing the next person who came in through the entrace each time he finishes an interview. MCQ

a) Case 1: Stratified sampling plan; Case 2: Non-probability sampling.

b) Case 1: Stratified sampling plan; Case 2: Systematic sampling plan.

c) Case 1: Cluster sampling plan; Case 2: Systematic sampling plan.

d) Case 1: Cluster sampling plan; Case 2: Non probability samplng.