PREP 上一道数学题。读不懂意思。。。关于标准差的。

奔三了 · 发表于 2011-8-13 23:02:51

说调查一个地区看电视的小时数，平均数是21，标准差是6，然后说，一个人（Pat），，，the number of hours that Pat, a resident of town X, watched television last week was between 1 and 2 standard deviation below the mean.求which of the following could be the number of hours that Pat watched television last week?