1. A telemarketer found that there was a 2% chance of a sale from his phone solicitations. If 1000 telephone calls were made, use the normal approximation to the binomial distribution to find the probabilities that

a) at most 20 sales were made;

b) more than 30 sales were made;

c) exactly 25 sales were made


2. The lengths of pregnancies of humans are normally distributed with a mean of 268 days and a standard deviation of 15 days. If 100 women are randomly selected,

a) find the mean and standard of error of the mean of the sampling distribution of sample means;

b) What happens to the mean and standard deviation of the distribution of sample means when the sample size is increased to 225?

c) Find the probability that the mean length of pregnancy, X (x bar)for a random sample of 100 women is more than 275 days

3. Commonly used practice of airline companies is to sell more tickets than actual seats to a particular flight because customers who buy tickets do not always show up for the flight. Suppose that the percentage of no shows at flight time is 3%. For a particular flight with 195 seats, a total of 200 tickets were sold. What is the probability that the airline overbooked this flight?