Which ones are cluster samples?

Check all that apply.
A. For a product-testing focus group, a company selects 10 men and 10 women at random from a population that has approximately equal numbers of both.
B. A school counselor selects 4 homeroom classes in her high school at random and gives them an attitude survey C. An airline chooses 30 of its 436 Boeing 737 flights on a certain day at random and administers a customer satisfaction questionnaire to every person on the chosen flights.D. A pollster wishes to survey voter preferences. In a county with 53,412 registered Democrats..

Question

Which ones are cluster samples? 

Check all that apply.
	A.	For a product-testing focus group, a company selects 10 men and 10 women at random from a population that has approximately equal numbers of both.
 B.	A school counselor selects 4 homeroom classes in her high school at random and gives them an attitude survey    C.	An airline chooses 30 of its 436 Boeing 737 flights on a certain day at random and administers a customer satisfaction questionnaire to every person on the chosen flights.D.	A pollster wishes to survey voter preferences. In a county with 53,412 registered Democrats..

anonymous · Answer

D.	A pollster wishes to survey voter preferences. In a county with 53,412 registered Democrats, 26,401 Independents, and 48,654 registered Republicans, she selects 42 Democrats, 21 Independents, and 38 Republicans at random for her survey sample.