本人最近在学习microeconometrics using stata，打算将课后题做出一份答案来，发现里面有不会做的，请大侠帮忙解决一下，第一章的第3题，那个log file不太明白，请大侠帮忙解答一下，谢谢！其他题答案如下：

*第1题答案
help clogit
search clogit
findit clogit
hsearch clogit

*第2题答案
sysuse auto,clear
by foreign:sum mpg weight
reg mpg weight foreign

*第3题答案

*第4题答案
sum price
return list
scalar cv=r(sd)/r(mean)

*第5题答案
reg mpg price weight
ereturn list
scalar r2adj=e(r2)-(1-e(r2))*(3-1)/(74-3)
mat best=e(b)
scalar bweight=best[1,1]
mat Vest=e(V)
scalar Vweight=Vest[1,1]
scalar tweight=bweight/sqrt(Vweight)
di "t statistic for H0: b_weight=0 is" tweight

*第6题答案
global varlist mpg price weight
sum $varlist
local varlist mpg price weight
sum `varlist'

*第7题答案
gen total=0
foreach v of varlist headroom length {
quietly replace total=total+`v'
}
sum total headroom length

*第8题答案
set obs 100
set seed 12345
gen x1var=runiform()
gen x2var=runiform()
sum x1var x2var