Introduction to Management Science 12th Edition by Bernard Taylor

Exercise 29

The owner of Gilley's Ice Cream Parlor has noticed that she sells more ice cream on hotter days during the summer, especially on days when the temperature is 85° or higher. To plan how much ice cream to stock, she would like to know the average daily high temperature for the summer months of July and August. Assuming that daily temperatures are normally distributed, she has gathered the following data for the high temperature for 20 days from a local almanac:
Compute the mean and standard deviation for these data and determine the expected number of days in July and August that the high temperature will be 85° or greater.