Use a Pareto chart of the effects to compare the relative magnitude and the statistical significance of both main and interaction effects. Minitab plots the effects in decreasing order of the absolute value of the standardized effects and draws a reference line on the chart. Any effect that extends past this reference line is significant. By default, Minitab uses an a-level of 0.05.

For the insulation data, there are two significant effects (a = 0.05):

·    One main effect - material type (A)

·    One interaction effect - material type by injection pressure (AB)

In addition, you can see that the largest standardized effect is material type by injection pressure (AB) because it extends the farthest.