clear
set more off

use "your path here\ncds_sel2.dta"

heckprob highedu fegp alvlperf iq siblings csex, select(alevel = fegp gce_74 iq siblings csex) iterate(30) technique(bfgs)
probit highedu fegp alvlperf iq siblings csex if alevel == 1

heckprob highedu fegp siblings csex, select(alevel = fegp siblings csex) iterate(30) technique(bfgs)
probit highedu fegp siblings csex if alevel == 1

heckprob highedu fedu alvlperf iq siblings csex, select(alevel = fedu gce_74 iq siblings csex) iterate(30) technique(bfgs)
probit highedu fedu alvlperf iq siblings csex if alevel == 1

heckprob highedu fegp fedu medu siblings csex, select(alevel = fegp fedu medu siblings csex) iterate(30) technique(bfgs)
probit highedu fegp fedu medu siblings csex if alevel == 1