For the following examples, write down the sampling method used in each situation.

• (a) A large company surveys 100 employees by taking random samples of 10 managers and 90 non-managerial employees.
• (b) Each student at a school has a student identification number. Counselors have a computer that generates 50 random identification numbers, and the students associated with those numbers are asked to take a survey.
• (c) A student council surveys 100 students by taking random samples of 25 freshmen, 25 sophomores, 25 juniors, and 25 seniors.
• (d) An airline company wants to survey its customers one day, so they randomly select 5 flights that day and survey every passenger on those flights.