Prep数学请教

黄公子

deviation的明白了，standard deviations前面加数字都是表示多少倍...看来deviation的题目都很少要你用公式去算，而是让你去通过mean和deviation的关系来计算阿

另外，139题，different看漏了还真不是第一次了，一定要仔细！

谢谢 坚定之路

liyilun54321

以下是引用坚定之路在2008-8-4 16:29:00的发言：

题目问的是which of the following values is more than 2.5 standard deviations from the mean? ，翻译成中文就是“下列哪个数值距离平均数的差值大于2.5倍标准差”，“距离”这个概念是指数轴上两点之间的长度。

这样解释，两位明白了吗？

崩溃~这英语也玩文字游戏！谢谢啦

梵尘

The question is a LOT simpler than it sounds. You're really being tested on your understanding of the definition of "standard deviation".

Standard deviation measures how numbers are spread out (relative to the mean) in a set. A high standard deviation means that numbers are very spread out; a low standard deviation means that numbers are packed tightly together around the mean.

Amber789

如果题106中有选项为28, 也是正确的吗? 还是有点晕.

Amber789

106.
                11122-!-item-!-187;#058&007588

If a certain sample of data has a mean of 20.0 and a standard deviation of 3.0, which of the following values is more than

2.5 standard deviations from the mean?

(A) 12.0

(B) 13.5

(C) 17.0

(D) 23.5

(E) 26.5

I think i now know why the answer is A for question 106.

2.5 SD = 7.5

2.5 SD = 7.5

2.5 SD from the mean (20.0) tells us the distance between Mean and SD is = 12.5

only the value less than 12.5 can yield a SD more than 7.5.

Searching for the answer, we find that only A can produce such a result(20-12=8).

梵尘

回14楼，

如果有28，应该也是对的。

黄公子

同意ls