The problem reads:

You work for the health dept. and it reports a 10% rate of STD for "at-risk" population. A contractor presents you with an unsolicited proposal for an intensive training program in an attempt to lower this rate. After running the program you perform a follow-up study of 150 individuals to determine if his program is effective. Assuming the program has no effect, find the mean and SD for the number of STD cases in groups of "at-risk" people.

What I think....

10% of 150 is 15, so 15 people have STD. But...is the mean the average of 15 or 150?

Plus, I'm not sure how to figure the SD on this. Any help or advice?

Thanks,

Tracy