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BUS 310, Homework #4, Spring 2018 Instructor: Betsy McCall

Instructions: Complete each problem on a separate worksheet in a single Excel file. Rename the separate worksheets with the respective problem number. You may have to copy and paste the datasets into your homework file first. Name the file with your last name, first initial, and HW #4. Label each part of the question. When calculating statistics, label your outputs. Submit your completed file in Blackboard.

1. Calculate the following probabilities using Excel, where is a -statistic with degrees of freedom.

a.

b.

c. Explain the difference between the probabilities in parts a and b.

d.

e. Explain the difference between this probability and the ones in a and b.

f.

g.

h. Explain the difference between the probabilities in part f and g.

i.

2. Find the value of or for each of the following scenarios.

a.

b.

c. Explain the difference between the values in parts a and b.

d.

e. Explain the difference between the value in d, and in parts a and b.

3. Use the data in the file 310homework4data.xlsx with data on repetitive task times for each of two workers. John has been doing this task for months, while Fred is just starting. Each time listed is the time (in seconds) to perform a routine task on an assembly line. The times shown are in chronological order.

a. Calculate a 95% confidence interval for the mean time it takes John to perform the task.

b. Calculate a 95% confidence interval for the mean time it takes Fred to perform the task

c. Do you believe both of the confidence intervals in parts a and b are useful or valid? Why or why not? Which worker would you rather have, all other things being equal?

4. Use the data in the file 310homework4data.xlsx with data on service times for a drive-up window at a fast-food restaurant. The file contains a random sample of 200 service times during the busiest part of the day.

a. Identify the relevant population.

b. Calculate the 95% confidence interval for the mean service time of all customers arriving during the busiest part of the day.

c. If the manager wants to improve service time during the busiest part of the day, does the confidence interval provide useful information? Why or why not?