According to a college survey, 22% of all students work full time. find the mean for the number of 3) students who work full time in samples of size 16.

Assuming that the students worldwide are being considered, because of the extremely large population, this can be considered as a binomial distribution. A normal distribution is used most usually as a fair approximation of the binomial. The mean is the expectation, therefore:
E[x] = np = (16)(0.22) = 3.52 
μ = 3.52 

he made 11 calls in one day