number of graduating students is a binomial variable, with p = 0.85, q = 1 - p = 0.15, n = 22
a) mean = n*p = 22 * 0.85 = 18.7
b) standard deviation = sqrt(n*p*q) = sqrt(22*0.85*0.15) = 1.67
p(x successes) = C(n,x) p^x q^(n-x) = C(22,x) 0.85^x 0.15^(22-x), where C(n,x) is the number of combinations of n item taken two at a time.
c) set x = 15 in above equation and compute probability
d) probability that at most 18 students attend college = 1 - probability more than 18 students attend college, set x to 18, 19, 20 , 21, 22 and compute probabilities, sum probabilities, then subtract from 1
e) set x to 15, 16, 17, 18, 19, 20, 21 and 22, compute and sum probabilities
