分类应为：制表问题求助
参：文献：，数据集：

“Table1 tabulates average callback rates by racial soundingness of names. Included inbrackets under each rate is the number of resumes sent in that cell. Row 1presents our results for the full data set.

Resumeswith white names have a 9.65 percent chance of receiving a callback. Equivalentresumes with African-American names have a 6.45 percent chance of being calledback. This represents a difference in callback rates of 3.2 percentage points,or 50 percent, that can solely be attributed to the name manipulation. Column 4shows that this difference is statistically significant[1]. Put in other words, theseresults imply that a White applicant should expect on average one callback forevery 10 ads she or he applies to; on the other hand, and African-Americanapplicant would need to apply to about 15 different ads to achieve the sameresult.”

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[1] Thesestatistical tests assume independence of callbacks. We have, however, verifiedthat the results stay significant when we assume that the callbacks arecorrelated either at the employer or first-name level.

此表初衷并非做描述统计量（比率、差异），实为比率检测proportion test， 具体点儿是，two sample proportion test for binary variable (here, the variable - call)

核心代码：
prtest varname if [..], by(groupvar)

另外，有个疑问：
如果有很多if条件，想编入个local宏，然后在循环里一个个代如，如何编辑这个local，那个引号老是不会加。