An auditor reviewed 20 oral surgery insurance claims from a particular surgical office, determining that the mean out-of-pocket patient billing above the reimbursed amount was $278.60 with a standard deviation of $78.98.

At the 5 percent level of significance, does this sample prove a violation of the guideline that the average patient should pay no more than $250 out-of-pocket?

(a-2)Calculate the test statistic.(Round your answer to 2 decimal places.)

Test statistic