PSAT Math Multiple-Choice Question 660: Answer and Explanation

Question: 660

A pollster wishes to project the winner for an upcoming election in her small city. Which of the following approaches to selecting a sample size would give the most accurate polling results?

• A. Interviewing randomly selected shoppers at the grocery store
• B. Contacting residents who live within half a mile of polling locations
• C. Contacting a random selection of registered voters
• D. Inviting voters to submit results to an online survey

Correct Answer: C

Explanation:

(C) A random sample is useful if it is truly random and if it is truly representative of the people being studied.

Choice (C) is correct because it polls a randomly selected group and takes into account only registered voters, which is what you would want to sample if you wanted to predict the results of an election.

Choice (A) is incorrect because it polls only people who go to that grocery store and likely excludes voters who shop elsewhere, are too elderly to shop, or don't have money to spend. It also likely samples a significant number of nonregistered voters who won't be counted in the election.

Choice (B) is incorrect because it polls only people in certain geographical locations and therefore likely people of only certain socioeconomic statuses as well.

Choice (D) is incorrect because it polls only those who have access to the Internet and actually take the time to complete the survey.