SAT Math Multiple Choice Question 860: Answer and Explanation

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Question: 860

5. Phase I clinical trials are run to determine the safety of all new drugs, especiallywith respect to the severity and duration of side effects. A physician is overseeinga Phase I trial based on 800 healthy participants. Half of the participants are giventhe drug, and half are given an inert pill. The mean duration of side effects forthose participants who were given the drug was 72 hours with a margin of error of6 hours. The physician is planning to replicate the trial in an attempt to decreasethis margin of error. Which of the following will most likely lead to a decrease inthe margin of error for the mean duration of side effects?

  • A. Decrease the trial size to 400 healthy participants.
  • B. Decrease the trial size to 400 participants, and replace half the healthy participantswith sick patients.
  • C. Increase the trial size to 1,600 healthy participants.
  • D. Increase the trial size to 1,600 participants, and replace half the healthy participantswith sick patients.

Correct Answer: C

Explanation:

C

Difficulty: Easy

Category: Problem Solving and Data Analysis / Statistics and Probability

Strategic Advice: Margin of error is a measure of data consistency. Think about how you could alter the sample pool for a study to decrease the margin of error.

Getting to the Answer: When conducting trials (or surveys), larger sample sizes lead to more reliable data. This, in turn, results in smaller margins of error. Therefore, the physician should increase the number of participants in the trial. Eliminate A and B. Replacing half the healthy participants with sick patients introduces another variable into the trial; consequently, doing this will prevent a valid comparison of the margins of error of the two trials. Choice (C) must be correct.

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