A university has found that 20% of its students withdraw without completing the introductory statistics course. Assume that 20 students have registered for the course this semester.
a) What is the probability that two or fewer will withdraw?
b) What is the probability that exactly four will withdraw?
c) What is the probability that more than three will withdraw?
d) What is the expected number of withdrawals?
e) Find the variance and standard deviation.