Robert Altoff is vice president for engineering for a manufacturer of household washing machines

Robert Altoff is vice president for engineering for a manufacturer of household washing machines. As part of new product development, he wishes to determine the optimal length of time for the washing cycle. A part of the development is to study the relationship between the detergent used (four brands) and the length of the washing cycle (18, 20, 22, or 24 minutes). In order to run the experiment 32 standard household laundry loads (having equal amounts of dirt and the same total weights) are randomly assigned to the 16 detergent—washing cycle combinations. The results (in pounds of dirt removed) are shown below.