The Resident of town X: GMAT Prep: PS

Anurag@Gurome: GMAT Instructor; Posts: 3835; Joined: Fri Apr 02, 2010 10:00 pm; Location: Milpitas, CA; Thanked: 1854 times; Followed by:523 members; GMAT Score:770

by Anurag@Gurome » Tue May 15, 2012 10:03 pm

Mean = 21 and S.D = 6

Number of hours that Pat watched television last week was between 1 and 2 standard deviations below the mean, and 1 S.D below the mean = mean - 1 * S.D = 21 - 6 = 15
2 S.D below the mean = mean - 2 * S.D = 21 - 12 = 9
This means that the number of hours that Pat watched television is between 9 and 15 hours, which is 12.

The correct answer is D.

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