Cube plots can be used to show the relationship between factors and a response. Each cube can show three factors. If there are only two factors, Minitab displays a square plot. Minitab draws as many cubes as necessary to show up to eight factors. You can draw a cube plot for two types of means:

·    Data means - the means of the response variable for the combinations of factor levels that are in the design.

·    Fitted means - after you analyze the design for a response, you can plot the fitted means for all combinations of factor levels.

For the insulation data, two cubes are used to represent the four factors. The cube on the left shows the response means when cooling temperature = 25. The cube on the right shows the response means when cooling temperature = 45. Use the fitted means on the cube plot to see the model predictions at all of the points in the design.

·     If Formula 2 is used, the injection pressure is high (150), injection temperature is high (100), and cooling temperature is low (25), the fitted mean of the strength of the insulation is 38.8526.

·    If Formula 1 is used, the injection pressure is high (150), injection temperature is low (85), and cooling temperature is high (45), the fitted mean of the strength of the insulation is 23.9115.