标题: 问一题8月JJ数学题 [打印本页] 作者: Jennywang2 时间: 2012-8-21 22:03 标题: 问一题8月JJ数学题 大概是说mean为86的一堆数里有百分之68的数标准方差是1，总的标准方差却是6，问92大约排在这堆数百分之多少的位置。作者: wtalan918 时间: 2012-8-25 10:20
112. Acertain characteristic in a large population has a distribution that is symmetric about the mean m. If 68 percent of the distribution lies within one standard deviation d of the mean, what percent of the distribution is less than m + d? (A) 16% (B) 32% (0 48% (D) 84% (E) 92%
Arithmetic Statistics
Since 68% lies between m- d and m+ d, a total of (100 - 68)% = 32% lies to the left ofm- d and to the right of m+ d. Because the distribution is symmetric about m, half of the 32% lies to the rightofm +d. Therefore, 16% lies to the right of m+ d, and hence (100 - 16)% = 84% lies to the left of m + d.