1. You work for a consumer advocate agency and want to find the mean repair cost of a

washing machine. As part of your study, you randomly select 40 repair costs and find the

mean to be $100.00. From past studies, you assume that the is $17.50.

a. Construct a 90% confidence interval.

b. Construct a 95% confidence interval.

c. Construct a 99% confidence interval.

2. The U.S. Dairy Industry wants to estimate the mean yearly milk consumption. A sample

of 16 people reveals the mean yearly consumption to be 60 gallons with a standard

deviation of 20 gallons.

a. What is the value of the population mean? What is the best estimate of this value

b. Develop the 90 percent confidence interval for the population mean.

c. Would it be reasonable to conclude that the population mean is 63 gallons?

3. The owner of the West End Kwick Fill Gas Station wishes to determine the proportion of

customers who use a credit card or debit card to pay at the pump. He surveys 100 customers

and finds that 80 paid at the pump.

a. Estimate the value of the population proportion.

b. Develop a 95 percent confidence interval for the population proportion

c. Interpret your findings