Time taken for oil change It is known that the amount of time needed to change the oil on a car is normally distributed with a standard deviation of 5 minutes. The manager of a service shop recorded the amount of time (in minutes) to complete a random sample of 10 oil changes. They are listed below.

11 10 16 15 18 12 25 20 18 24

1. The sample average is: _______ minutes (up to 2 decimal points)

2. The sample standard deviation is: _______ minutes (up to 2 decimal points)

3. Compute a 95% interval estimate of the population mean.

4. Lower Confidence Level ___ Minute (up to 2 decimal points)

5. Upper Confidence Level ___ Minutes (up to 2 decimal points)

6. Based on your answer above, if you take your car to this particular shop, your car will be serviced between _____ and _____ minutes. You are _____ % certain about this.

(Round to whole numbers for the purpose of marketing. 1.3 is rounded as 1; 1.6 is rounded as 2. Put the smaller number in the 1st blank and the larger number in the 2nd blank)

7. Suppose that the manager feels that the range of values he obtained above are too wide to attract customers. What can he do to obtain a narrower range of values?

Group of answer choices

a. Use a 90% confidence interval

b. Take a random sample of 100 oil changes

c. Train his employees well so that the variability in time to change oil reduces

d. All the above

e. None of the above

Answer rating: 100% (QA)

1 2 3 4 5 6 Solution We have X time taken for oil change X is is normally distributed with standard ... View the full answer