Question

一道GRE数学题 ！

In a normal distribution, 68% of the scores lie within one standard deviation of the mean. If the SAT scores of all the high school juniors in Center City followed a normal distribution with a mean of 500 and a standard deviation of 100, abd if 10,200 students scored between 400 and 500, approximatedly how many students scored above 600?

Answer 1

在一个正常的分布，的分数68%是一个平均值的标准偏差。如果SAT考试的所有高中生在中心城市后的平均值为500，标准差为100的正态分布，而如果10200的学生取得了400和500之间，大约有多少学生得分高于600？

追问

谢谢了，其实题目我还是基本看得懂，但是神马标准偏差的，正态分布的，忘了，能细讲下解题思路吗

追答

我还没有学，只能把题目翻译了

Answer 2

since it's a normal distribution, 68% of the scores lie within one standard deviation of the mean
, the standard deviation of 100, and the mean is 500, which means the number of people scored bw 400 and 500 is the same as the number of people scored bw 500 and 600. Both are 10,200. Therefore, 10,200*2=20,400 people are within one SD, which is 68% of the whole population. So we can get the whole poplulation of 30,000. people above 600 is the same number as people below 400, that is (30000-20400)/2=4800.

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