Suppose a researcher is interested in the average ACT score for high school students in Illinois. She randomly selects 20 counties and then randomly selects 3 high schools from each selected county and then asks each student in the selected high schools what their ACT score was. What kind of sample is this?

Multistage sampling D

Explanation:

The researcher used two-stage cluster sampling method; the researcher first selected randomly 20 counties from all the counties, then the researcher selected a subgroup of 3 high schools from each selected county and sample all the students in it. If it single-stage cluster sampling, the researcher randomly select a group from the large group and sample all the element.

There is also another type of cluster sampling called multi-stage sampling. This a sample method in which the researcher first divide the population into districts, from the district, a group is randomly selected, from the smaller group is again selected.

Simple Random sample

Explanation:

A simpe random sample is used to represent an unbiased sample of a group. in this type of sample, every member has an equal chance of being selected.