AP Statistics : How to do random assignments in an experiment

Study concepts, example questions & explanations for AP Statistics

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Example Questions

Example Question #2 : How To Conduct An Experiment

A researcher wants to randomly assign participants to a treatment and control group. Which of the following approaches ensures that the treatment assignment is random?

Possible Answers:

Assigning the treatment by gender

Flipping a coin

Assigning the treatment based on who needs it the most 

Obtaining nationally representative samples for both

Correct answer:

Flipping a coin


The only random procedure here is the coin flip. In expectation, the coin flip ensures that no background variables influence treatment assignment whereas the other examples either have nothing to do with random assignment (e.g. nationally representative sample) or completely contradict the purpose of random assignment (e.g. assigning the treatment based on who needs it the most). 

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