For Exercise 4.109, see page 220; for 4.110, see page 223; for 4.111 to 4.114, see page 228; for 4.115, see page 230; and for 4.116 to 4.118, see page 235.
4.116 Comparing sales.
Tamara and Derek are sales associates in a large electronics and appliance store. Their store tracks each associate's daily sales in dollars. Tamara's sales total varies from day to day with mean and standard deviation
Derek's sales total also varies, with
Because the store is large and Tamara and Derek work in different departments, we might assume that their daily sales totals vary independently of each other. What are the mean and standard deviation of the difference between Tamara's daily sales and Derek's daily sales? Tamara sells more on the average. Do you think she sells more every day? Why?