***********************************************************************
* This is a program that illustrates the use of PROC POWER to         *
* calculate sample size when comparing two normal means.              *
***********************************************************************;

proc power;
twosamplemeans dist=normal groupweights=(1 1) alpha=0.05 power=0.9 stddev=0.75 
   meandiff=0.25 test=diff sides=2 ntotal=.;
plot min=0.1 max=0.9;
title "Sample Size Calculation for Comparing Two Normal Means (1:1 Allocation)"; 
run;

proc power;
twosamplemeans dist=normal groupweights=(2 1) alpha=0.05 power=0.9 stddev=0.75 
   meandiff=0.25 test=diff sides=2 ntotal=.;
plot min=0.1 max=0.9;
title "Sample Size Calculation for Comparing Two Normal Means (2:1 Allocation)"; 
run;