UW Data Analytics T Test Two Sample Assuming Equal Variances Questions – Description
The Greenwich branch of Tesco, a groceries and general merchandise retailer, are examining their delivery data. Most of their deliveries are within a 10-mile radius, but they occasionally deliver to customers more than 10 miles away. Tesco employs a number of delivery people, four of whom are relatively new hires. The grocery chain has recently been receiving customer complaints about excessively long delivery times. Therefore, Tesco Greenwich has collected data on a random sample by its four new delivery people during peak delivery times. The data are in the tab titled “Problem_3_Data”. The variables are: Deliverer: which person made the delivery; Prep Time: time from when order was places until delivery person started driving it to customer; Travel Time: time to drive from Tesco to customer; Distance: distance (miles) from Tesco to customer. Greenwich Tesco is concerned that one or more of the new delivery people might be slower than others.
a. Let Di and Ti be the mean delivery time and mean total time for delivery person i, where the total time is the sum of the delivery and perp times. Calculate 95% confidence intervals for each of these means for each delivery person. Although these might be interesting, give two reasons why they are not really fair measures for comparing the efficiency of the delivery people.
b. Responding to criticism in part a, calculate a 95% confidence interval for the mean speed of delivery for each delivery person, where speed is measured as miles per hour during the trip from Tesco to the customer. Then calculate 95% confidence intervals for the mean difference in speed between each pair of delivery people.
c. Write a report of your findings, including any recommendations you would make to Tesco.
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