A kinesiology professor, requiring volunteers for her study, approaches students one by one at a campus hub. She will continue until she acquires 40 volunteers. Suppose that 25% of students are willing to volunteer for the study, that the professor’s selections are random, and that the student population is large enough that individual “trials” (asking a student to participate) may be treated as independent.

a. What is the expected number of students the kinesiology professor will need to ask in order to get 40 volunteers? What is the standard deviation?
b. Determine the probability that the number of students the kinesiology professor will need to ask is within one standard deviation of the mean.