数学机经的一题

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116. 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。

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OG原题供参考

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.

The correct answer is D.