Power Estimate with Standard Deviation Percentage Difference

[mekono]

I want to estimate the power associated with various treatment effects between two groups. In group 1 there are 145 people and group 2 has 225 people. Additionally, I expect the average score of group 1 to be 31% and group 2 41%.  Based on previous studies, we expect a 5% standard deviation in each cohort. How can I incorporate 5% sd into my power estimate?

Originally, I estimated power this way:

proc power;
twosamplemeans test=diff
groupmeans = 0.31 | .41
stddev = 0.05
groupns= (145 225)
power = .;
run;

Is this correct or should I take another approach? 

[sbxkoenk · Accepted solution]

Same question as posed in the 'Statistical Procedures' board under Analytics header.

See here:
https://communities.sas.com/t5/Statistical-Procedures/Power-Estimate-with-Standard-Deviation-Percent...

Koen