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  3. The distribution of the numbers of hours that students at a certain college studied for final exams has a mean of 12 hours and a

The distribution of the numbers of hours that students at a certain college studied for final exams has a mean of 12 hours and a

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问题 The distribution of the numbers of hours that students at a certain college studied for final exams has a mean of 12 hours and a standard deviation of 3 hours. Which of the following numbers of hours are within 2 standard deviations of the mean of the distribution?
Indicate all such numbers.
A 2
B 5
C 10
D 14
E 16
F 20
选项
答案C，D，E
解析 Given that the mean of the distribution is 12 hours and the standard deviation is 3 hours, the numbers of hours within 2 standard deviations of the mean are all numbers of hours between 12 - 2(3), or 6, and 12 + 2(3), or 18. Thus the correct answer consists of Choices C, D, and E.
This explanation uses the following strategy.
Strategy 1: Translate from Words to an Arithmetic or Algebraic Representation
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