In Problem 13.7 on page 531, you used the number of customers to predict the waiting time at a supermarket checkout. Perform a residual analysis for these data (stored in Supermarket). Based on these results, evaluate whether the assumptions of regression have been seriously violated.
In problem
A critically important aspect of customer service in a supermarket is the waiting time at the checkout (defined as the time the customer enters the line until he or she is served). Data were collected during time periods in which a constant number of checkout counters were open. The total number of customers in the store and the waiting times (in minutes) were recorded. The results are stored in Supermarket.