power analysis: calculate the sample size needed

[Lindy]

Could any one please provide me with the SAS code I should use for this task?

The rate of a type of disease in the general population is 50%, and I am giving a group of randomly selected people a type of vitamin to observe if the vitamin can decrease the rate of disease in this treatment group. I want to be able to identify the significant effect as long as there is 40% rate of this disease in my treatment group at alpha .05 and power .80. What sample size minimally I should have?

Thank you so much!

[PGStats]

Use proc power with statement onesamplefreq.Specify PROPORTION=0.4 and NULLPROPORTION=0.5. Read the documentation.