Suppose that the number of customers who enter a supermarket each hour is normally distributed with a mean of 540 and a standard deviation of 150. The supermarket is open 14 hours per day. What is the probability that the total number of customers who enter the supermarket in one day is greater than 7200? (Hint: Calculate the average hourly number of customers necessary to exceed 7200 in one 14-hour day.)

Answer 1

You need an average of 514.3 per hour to have 7200 in 14 hours. So, use a normal distribution to find the probability of getting 514 or more per hour, when the mean is 540 and the std. dev. is 150.

I get a value of 56.8%, using a computation tool at
http://psych.colorado.edu/~mcclella/java/normal/accurateNormal.html