Question: Identify the sampling technique used to obtain a sample in each of the following. Explain why you chose the sampling technique you did for each.

a. Every 20th washing machine coming off an assembly line is checked for defects

b. District supervisors are selected using random numbers in order to determine annual salaries.

c. Students at a local university are classified according to their major. Then a random sample of 20 students from each major is selected.

d. The first 40 people entering a supermarket are asked their opinion on the price of cooking oil.

e. A state is divided into regions using zip codes. A random sample of 30 zip code areas is selected.