Approximate the probability of less than 90 infant deaths in a sample of 1000 births, if the infant mortality rate is 0.10.
P(X<90)
Expected number is .1*1000 = 100
SD is sqrt(n*p*q) = 1000*.1*.9 = 9.49
90 is 10 away from the mean and 10/9.48= 1.05 standard deviations away. Your stats book should have a cumulative normal distribution table. look up 1.05. I get .8531.
Ergo, the probability of seeing more than 90 is 85.31%
take it from here