Classify the situations in questions 2 to 4 as stratified random sampling, systematic random sampling, or cluster sampling.

A college decided to survey its students to see how they felt about using a computer in all classes, and how much extra tuition they would be willing to pay for the service.

2.The college made a list of all of the classes registered in the semester and then randomly selected 25 classes. All students in the selected 25 classes were surveyed.

3.The college determined that of its 10 000 students, 500 surveys would be sufficient to achieve satisfactory results. The students attending in that semester were sorted according to their student number, and every 20th student on the list was selected for the survey.

4.The college decided to survey the students according to their programs of study. A random sample was selected from each program.