8(11)

Some accounting firms give the client an option to pay a fee when the tax return is completed that guarantees tax advices and support from the accountant if the client were audited. A large accounting firm is trying to determine what fee to charge for next year's returns. In previous years, the actual mean cost to the firm for attending a client audit session was $720. To determine if this cost has changed, the firm randomly samples 35 client audit fees. The sample mean audit cost was $680 with a standard deviation of $85. Complete parts a and b below. a) Develop a 95% confidence interval estimate for the mean audit cost. The 95% confidence interval for the mean audit cost is ($ 651 ,$ 709 (Round to the nearest dollar as needed.) b) Based on your confidence interval, what do you think of the claim that the mean cost has changed? O A. The interval contains the historical mean $720, which supports the claim that the mean cost has changed. O B. The interval does not contain the historical mean $720, which does not support the claim that the mean cost has changed. O C. The interval contains the historical mean $720, which does not support claim that the mean cost has changed. O D. The interval does not contain the historical mean $720, which supports the claim that the mean cost has changed