Use a simplex design plot to visualize the mixture design space (or a slice of the design space if you have more than three components). Minitab plots the design points on triangular axes. You can plot the following:

·    components only

·    components and process variables

·    components and an amount variable

The display depends on whether the design contains process variables or an amount variable, and how you choose to handle these variables. You can display a plot that shows all the levels of these extra variables (as shown here) or just display a single plot.

For the fondue data, a constrained extreme vertices design was chosen to investigate the effects of blend and serving temperature on flavor. Because there is one process variable (Temperature), a triangular plot is generated for each level of Temperature. The simplex design plot shows the shape of constrained design region and the 18 design points that are in this region. The points are as follows:

·    Eight vertices: These are the points at the "corners" of the design space. There are four vertices at each level of Temperature for a total of eight points.

·    Two center points: These are the points at the center of the design space, which correspond to the blend in which the component proportions are the averages of the corresponding vertex proportions. There is one center point at each level of Temperature for a total of two points.

·    Eight axial points: These are the points on the interior of the design space that lie exactly halfway between the center point and a vertex. There are four axial points at each level of Temperature for a total of eight points.