* Sample Size and Power do file
* Wayne Enanoria
* 8 September 2015

* Change the working directory
cd "/Users/wtaeuser/Dropbox/Documents/courses/Biostat212/2015/week7talk"/Users/wtaeuser/Dropbox/Documents/courses/Biostat212/2015/week7talk


* Sample Size Calculations

power twomeans 100 125, power(0.80) sd1(15) sd2(17)

power twomeans 100 125, power(0.80) sd1(15) sd2(17) graph

power twomeans 100 (102(1)125), power(0.80) sd1(15) sd2(17) graph

power twomeans 100 (102(1)125), power(0.80) sd1(15) sd2(17)

power twomeans 100 (102(1)125), power(0.80) sd1(15) sd2(17) saving("sampsize1.dta")

power twomeans 100 (102(1)125), power(0.80(0.05)0.9) sd1(15) sd2(17) graph graph(nosimplelabels legend(title("Power")))



* Power analysis

power twomeans 100 125, sd1(15) sd2(17) n(10)

power twomeans 100 125, sd1(15) sd2(17) n(10) graph


* Fixed sample size, vary effect size
power twomeans 100 (102(1)140), sd1(15) sd2(17) n(10) graph

power twomeans 100 (102(1)140), sd1(15) sd2(17) n(10) saving("sampsize2.dta")


* Fixed effect size, vary sample size
power twomeans 100 125, sd1(15) sd2(17) n(6(2)20) graph