Overview for Create Mixture Design

Use Create Mixture Design to create a designed experiment when the response depends on the relative proportions of mixture components, such as the ingredients in bread dough. Minitab provides three design types, including simplex centroid, simplex lattice, and extreme vertices designs. You can also include process variables or an amount variable in the design. For more information, go to What is a mixture design?, Choose a mixture design, and What is an extreme vertices design?.

When you create a design, Minitab stores the design information in the worksheet, which shows the order in which data should be collected. Once you have collected your data, use Analyze Mixture Design to analyze the data.

For example, researchers want to study how the proportions of three ingredients in a household deodorizer affect the acceptance of the product based on scent. The three components are neroli oil, rose oil, and tangerine oil. The researchers use a simplex centroid design to study the effects of the three components.

This Minitab worksheet shows a portion of the simplex centroid design. Neroli, Rose, and Tangerine are the components. The values in these columns are the mixture proportions. In this design, the proportions in each row sum to 1. The researchers perform the experiment by collecting data using the order shown in the RunOrder column.

C1 C2 C3 C4 C5 C6 C7
StdOrder RunOrder PtType Blocks Neroli Rose Tangerine
10 1 -1 1 0.16667 0.16667 0.66667
5 2 2 1 0.50000 0.00000 0.50000
3 3 1 1 0.00000 0.00000 1.00000
7 4 0 1 0.33333 0.33333 0.33333
6 5 2 1 0.00000 0.50000 0.50000
4 6 2 1 0.50000 0.50000 0,00000
8 7 -1 1 0.66667 0.16667 0.16667

After collecting the data, a scientist enters the response data in an empty column in the worksheet and then, analyzes the design.

Many of the choices you make when you create a design depend on your overall experimental plan. For more information, go to Phases of a designed experiment.

Where to find this analysis

Stat > DOE > Mixture > Create Mixture Design

When to use an alternate analysis

  • If your design does not involve different formulations of a mixture, you should determine which design type is most appropriate for your data.
  • If you already have mixture components in a worksheet, use Define Custom Mixture Design. Custom designs let you specify which columns are the components and any other design columns that you have.
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