题目是这样的。4.15 Does the return to education differ by race and gender? For this exercise, use the filecps4.dat. In this exercise you will extractsubsamples of observations consisting of (i) all males, (ii) all females, (iii) all whites,(iv) all blacks, (v) white males, (vi) white females, (vii) black males, and (viii) blackfemales.
(a) For each sample partition, obtain the summary statistics of WAGE

用的STATA。前面4个子样本我会提取，就是summarize wage if female 之类的
但是后面四个比如 white males 我理解的就是 summarize wage if ~female&~black，但是做出来总是和答案不一样。
我做出来的均值是22.66441，但是答案上的均值是22.500。晕倒
求助各位大佬们