Question

Among employed women, 25% have never been married. Select 10 employed women at random. What is the mean number of women in such a sample who have never been married? What is the standard deviation?

I think the mean would be 2.5, but I'm not sure about the standard deviation.

Answer 1

probability that the women was unmarried = p = 0.25
probability that she was married = q = 1-p = 0.75
sample size , n = 10
mean = np = 10 x 0.25 = 2.5
standard deviation = sq. root (npq)
=1.37