Safegate foods, inc., is redesigning the checkout lanes in its supermarkets throughout the country and is considering two designs. tests on customer checkout times conducted in two stores where the two new systems have been installed result in the following summary of the data: system a system b size 120 100 mean 4.1 minutes 3.4 minutes standard deviation 2.2 minutes 1.5 minutes test at the 0.05 level of significance to determine whether the population mean checkout times of the two systems differ. which system is preferred?

use both the critical and p-value approach.

hypotheses:

decision rule:

calculations:

conclusions: