7 the sampling distribution of X-X, cannot be assumed normal, we are unable to compute a confidence interval are still able to use the z distribution to compute a confidence interval must use the tar distribution with n+n2-2 degrees of freedom to compute a confidence interval Omust use the tar distribution and calculate the degrees of freedom using n, n2, S1, and 52 to compute a confidence interval D Question 8 A car dealer who sells only late-model luxury cars recently hired a new salesperson and believes that this salesperson is selling at lower markups. He knows that the long-run average markup in his lot is $5,300. He takes a random sample of 25 of the new salesperson's sales and finds an average markup of $4,700 and a standard deviation of $840. Assume the markups are normally distributed. What is the value of an appropriate test statistic for the car dealer to use to test his claim? O2--0.75 124 -3.57 124 -0.75 z=-3.57