Outcomes: conduct a test of hypothesis for two independent population means. Use separate-variance t test when unequal s are known s and s are unknown and s are unknown but equal s and. Ryerson car magazine is comparing the total repair costs incurred during the first three years on two sport cars, the r123 and the s456. Random samples of 45 r123 cars are for the first three years. Assume that the standard deviations for the two populations are and , respectively. 1 m be the population mean repair cost for sport car r123 m be the population mean repair cost for sport car s456. Since the p-value > 0. 05, do not reject the null hypothesis. There is not enough evidence to conclude that such mean repair costs are different for these two types of cars. Mark is the owner of the appliance patch.