A certain 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 distribution that is symmetric about the mean M: 50% is less than M
68% of the distribution lies within one standard deviation D of the mean: 34% is between M - D, and 34% is between M and M + D
so 50% + 34% = 84% is less than M + D.唐卫公 | 十六级
应该是对的， 如果后来人也看了这道题，可以参考一下～
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发表于 2009-6-24 18:14:00
...请教思路和步骤~~谢谢~~
