AP Statistics : How to do stratified random sampling

Study concepts, example questions & explanations for AP Statistics

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Example Questions

Example Question #1 : How To Do Stratified Random Sampling

Which of the following is an example of stratified random sampling when obtaining a sample of  high school students? 

Possible Answers:

Choosing  students at random from a high school 

Choosing  students at random from a specific grade level at a high school

Choosing  students at random from an AP Statistics class at a high school 

Choosing  students sitting in one random section of the cafeteria at a high school

Choosing  students at random from each of four different grade levels at a high school

Correct answer:

Choosing  students at random from each of four different grade levels at a high school

Explanation:

In order for there to be a stratified random sample, the target population must be split into different groups (i.e. grade levels). The sample population must be selected at random from each of these groups (i.e. choosing  students from each of four different grade levels or groups). The other examples, although random, are not specifically stratified in their sampling methodology. 

Example Question #2 : How To Do Stratified Random Sampling

A study testing the effect of caffeine on mental performance invited  participants for an experiment. The participants were selected randomly.  people were selected from men who did not drink coffee.  were selected from women who did not drink cofee.  were selected from men who regularly drank coffee, and  from women who regularly drank coffee. What type of sampling method is this?

Possible Answers:

Group Sampling

Stratified Random Sampling

Convenience Sampling

Systematic Sampling

Simple Random Sampling

Correct answer:

Stratified Random Sampling

Explanation:

Stratified Sampling is the method of randomly selecting subjects from various stratum, or subsets of the population. In this case, there were 4 stratum from which participants were randomly selected.

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