Question: A manufacturer uses two different trucking companies to ship its merchandise. The manufacturer suspects that one company is charging more than the other and wants to test it. A random sample of the amounts charged for one truckload shipment from Chicago to Detroit on various days is collected for each trucking company. The data (in dollars) is given below.
a. Assuming that the two populations are normally distributed with equal variance, test the null hypothesis that the two companies' average charges are equal.
b. Test the assumption of equal variance.
c. Assuming unequal variance, test the null hypothesis that the two companies' average charges are equal.