Industrial Statistics with Minitab

28.3 Contour Plots and Response Surface Plots

When drawing the contour plots or response surfaces on the model chosen, you can only use 2 factors (one for each of the axes X and Y). The remaining factors should be set to one of their levels. A couple of suggestions are:

• If a factor is involved in a model in a quadratic form, it should be included as one of the axes.
• If a factor takes only a few values, a good idea is to produce a graph with other two factors for each of this levels.

Stat > DOE > Response Surface > Contour/Surface Plots

In our example, the variables T and Co1 are used for the axes, and the variable Co2 is set to its low, medium and high values. Since the variable rpm is not involved in the model, we should not worry about it.

The following graphs show the contour plots and the response surfaces while maintaining the factor Co2 at its low, middle, and high level.

Minitab draws contour plots and response surfaces of the latest model produced using Analyze Response Surface Design. It is not possible to memorize models and then draw them.

The surface ...