Im using stata for this power analysis and cannot figure it

I\'m using stata for this power analysis and cannot figure it out.

An investigator is planning a grant application to study the whether patients involuntarily placed in an alcohol rehabilitation program, on average, exceed one criteria for depression diagnosis. The researcher intends to interview subjects using the Center for Epidemiologic Studies Depression scale (CESD) where a conventional cutoff for depression is a score of 20 or higher. The investigator assumes that a meaningful difference is 1 point and that the expected standard deviation is 2. How many subjects will the investigator need to recruit for an alpha level of 0.05, a power of 0.9, and no dropout. How many subjects should be recruited?

A - 36

B - 41

C - 46

D - 55

Solution