Official Guide Explanation:
Problem Solving #199

Background

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Solution and Metadata

Question: 199
Page: 180
Difficulty: 5 (Moderate)
Category 1: Arithmetic > Descriptive Statistics > Standard Deviation

Explanation: You'll never need to know how to solve for standard deviation on the GMAT, but you do need to know the basics of how its calculated. Standard deviation is little more than the average of each term's difference from the mean. So, II has a standard deviation of zero: all the terms in the set are the same. I has a small standard deviation: no term is more than 2 away from the mean. III has a greater standard deviation: while three of the terms are the same, the other two are much farther from the mean. Without any calculation, that means III's SD is greater than I's SD, which is greater than II's SD, choice (D).

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