use "http://wps.aw.com/wps/media/objects/3254/3332253/datasets2e/datasets/TeachingRatings.dta", clear
gen age_sq=age*age
gen fem_beauty=female*beauty

reg course_eval beauty intro onecredit female minority nnenglish, vce(hc3)
reg course_eval  beauty intro onecredit female minority nnenglish age age_sq, vce(hc3)
test (age age_sq)

reg course_eval beauty intro onecredit female minority nnenglish fem_beauty, vce(hc3)
test fem_beauty

summarize beauty
scalar md_L = r(mean)-r(sd)
scalar md_U = r(mean)+r(sd)
scalar d_B = 2*r(sd)
scalar list md_L md_U d_B

reg course_eval  beauty intro onecredit female minority nnenglish  fem_beauty, vce(hc3)
scalar lb = d_B*_b[beauty]-1.96*_se[beauty]*d_B
scalar ub = d_B*_b[beauty]+1.96*_se[beauty]*d_B
scalar list lb ub

lincom beauty+fem_beauty
scalar lb2 = d_B*r(estimate)-1.96*r(se)*d_B
scalar ub2 = d_B*r(estimate)+1.96*r(se)*d_B
scalar list lb2 ub2