A fast-food company is interested in examining whether reducing the number of menu items will increase revenue. Before rolling out the new menu nationwide, the company wants to test it in some select markets. The company decides to examine the southwest region first. Using the data base that contains information on the locations of all of its franchisees' stores, the company randomly selects a collection of 50 stores. Of the 50, half were given the new menu and half were told to continue using the old menu. Sales from the stores in both groups were tracked for six weeks. After analyzing the data, management concluded, with a high degree of confidence, that using the new menu nationwide would increase revenue by an average of 20 to 30 percent, This conclusion is an example of a (an) .