TT2-4求教

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.

找到了,标准方差:每个数减去平均数的偏差的平方,除以N,最后开根号

特征: 数据分布离平均值越近,标准方差越小,数据分布离平均值越远,SD越大

GMAT中从来不要求你算具体的标准方差，就是让你

（1）比较两个标准方差的大小。

（2）让你确定根据条件可不可以确定标准方差。

你只要知道它的概念就可以做题了。