Retail chain Kroger has more than locations and is the largest supermarket in the United States based on revenue. Kroger has invested heavily in data, technology, and analytics. Feeding predictive models with data from an infrared sensor system called QueVision to anticipate when shoppers will reach the checkout counters, Kroger is able to alert workers to open more checkout lines as needed. This has allowed Kroger to lower its average checkout time from four minutes to less than seconds $($Retail Touchpoints$).$

Consider the data in the file Checkout. The file contains observations. Each observation gives the arrival time $($measured in minutes before p$.$m$.)$ and the shopping time $($measured in minutes$).$