Question: The Tires and Auto department at Costco installs new tires. In order to provide good customer service, the manager of a Costco store want to determine the average time it takes to install a set of four new tires at the shop. Assume that the standard deviation of the time taken to install four new tires is known from historical records to be 4.25 minutes.

1. After measuring the time taken to install four new tires on 50 vehicles, the manager found that their average time was 19.45 minutes. Construct a 93% confidence interval for the average time taken to install four new tires.
2. How many tire installations should be observed in this study (i.e. what sample size do you need) in order to have the mean installation time estimated up to a 45 second precision with 93% confidence? {45 second precision means you will be within ±45 seconds of the true mean}
3. What is the population for which inferencing was done in part (a)?

Price: $2.99

Solution: The downloadable solution consists of 2 pages
Deliverable: Word Document