[推荐]标准方差的总结

wyoung · 发表于 2012-1-11 23:09:10

很好本月340题用到了感谢

ptlove4ever · 发表于 2012-1-11 23:10:14

Is the standard deviation of the salaries of Company Y’s employees greater than the standard deviation of the salaries of Company Z’s employees?
(1)   The average (arithmetic mean) salary of Company Y’s employees is greater than the average salary of Company Z’s employees.
(2)   The median salary of Company Y’s employees is greater than the median salary of Company Z’s employees.

A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
D. EACH statement ALONE is sufficient.
E. Statements (1) and (2) TOGETHER are NOT sufficient.

diana32686 · 发表于 2012-3-14 14:30:30

thx!

李春阳 · 发表于 2012-8-11 06:09:55

所以说如果有一系列数xi，i=0，1，2，.....n, 然后xi中的每一个数乘以m
Mean（m*xi）=m*Mean（xi）

Variance（m*xi）=m^2*Variance（xi）

St. D（m*xi）=sqrt（（Variance（m*xi））=sqrt（（m^2*Variance（xi））=sqrt（m^2)*sqrt（Variance（xi））=m*St.D（xi）

是这样，对不对？

夏夏公主9797 · 发表于 2012-8-11 10:26:43

Yanners · 发表于 2012-8-11 11:29:56

谢谢啊，记下了！

小兔0116 · 发表于 2012-8-11 11:38:10

thanks~~

ericaikg · 发表于 2012-8-24 15:25:57

sunny20111126 · 发表于 2012-8-24 19:05:12

crystal1991xy · 发表于 2012-11-1 07:48:47

[推荐]标准方差的总结

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