求助 TT GWD31 18-18

xdffans

Q18:

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.     16%

B.     32%

C.     48%

D.     84%

E.      92%

这道题目答案是D。请问是怎么想的呀？

yalemba2007

题目问的是多少分布是少于m+d的, 68%在d里, 32%分布在d外, 由于是对称分布,  16%>m+d, 所以84%小于m+d.

麻烦LZ看看我的问题:

http://forum.chasedream.com/dispbbs.asp?boardID=22&ID=205794&page=1

xdffans

抱歉，还是不懂。这道题目也看不太懂。。。

yalemba2007

找个图给你看看, 中间那根最高线是M, 左右两边的线分别就是M-D和M+D.大于M+d和小于M-D的分布都是16%, 两者中间的分布是68%.

http://images.google.com/imgres?imgurl=http://coe.sdsu.edu/eet/Articles/standarddev/SD-chart-lines-fixed.jpg&imgrefurl=http://coe.sdsu.edu/eet/Articles/standarddev/start.htm&h=254&w=500&sz=10&hl=en&start=2&tbnid=6rU6A3u-WKHwqM:&tbnh=66&tbnw=130&prev=/images%3Fq%3Dstandard%2Bdeviation%26svnum%3D10%26hl%3Den%26lr%3D

xdffans

好厉害！我懂啦。谢谢！

uglysusan

TT 是什么意思？

xdffans

TT GWD，就是“涛涛GWD”.

是GWD的一个版本，共31套题目。

danver

涛涛  TT  是 Total, I think.