Before you use Minitab, you need to determine what design is most appropriate for your experiment. Minitab provides simplex centroid, simplex lattice, and extreme vertices designs.
When you are choosing a design you need to do the following steps:
To help you visualize a mixture design, the following figures show design points using triangular coordinates. Each point on the triangle represents a specific blend of components that you would use in your experiment. For simplicity, the figures show three component designs. The following diagrams only show a few of the mixture designs you can create. Minitab can also create simplex lattice designs up to degree 10 and extreme vertices designs.
Unaugmented | Augmented | |
Simplex Centroid | ||
Simplex Lattice Degree 1 | ||
Simplex Lattice Degree 2 | ||
Simplex Lattice Degree 3 |
When selecting a design, it is important to consider the maximum order of the fitted model required to adequately model the response surface. Mixture experiments frequently require a higher-order model than is initially planned. Therefore, when possible, conduct additional runs beyond the minimum required to fit the model.