Specify the terms to use in your model. Minitab includes a set of terms based on the model that you specify, or you can choose the terms directly from the list of all available terms.
- Factorial design
- In Include terms in the model up through order, select the maximum order for terms to include in the model. Minitab puts these terms in the list of selected terms.
- For example, if you select 2, then Minitab puts all main effects and two-way interactions in Selected Terms. Main effects and higher-order interactions are in Available Terms.
- Response surface design
- In Include the following terms, select linear, linear and squares, linear and interactions, or a full quadratic model.
- For example, if you select Full quadratic, then Minitab moves all main effects, two-way interactions, and square terms from Available Terms to Selected Terms.
- Mixture design
- In Include component terms for model, select linear, quadratic, special cubic, full cubic, special quartic, and full quartic.
- For example, if you select Linear, then Minitab puts all main effects from Available Terms to Selected Terms.
- Check Include inverse component terms to include all inverse component terms in the model. Inverse terms are not available for components that include the value 0 in the candidate set.
- Available Terms
- The list of all terms up to the maximum order that Minitab provides for the number of factors in the design. Interaction terms are in Available Terms unless they are in Selected Terms.
- Selected Terms
- The list of the terms that Minitab uses in the model.
Use the arrow buttons to add and remove terms.
- Move the terms that you selected in the Available Terms list to the Selected Terms list.
- Move all terms in Available Terms to Selected Terms.
- Remove the terms that you selected in the Selected Terms list from the model.
- Remove all terms from the model.
With a factorial design, you can use the Cross
buttons to add interactions and default terms.
- Put the interaction between the main effects that you select in Available Terms in Selected Terms. For example, select the A, B, C, and D main effects in Available Terms, then click Cross to put the 4-way interaction (ABCD) among these factors in the model.
- The default factors are all of the terms up to the order that has fewer than 127 total terms, the highest number of terms that can be in the model. For a general full factorial design with 2 to 7 factors, the default order is the same as the number of factors. For 8 factors, the default is all terms up to order 3. For 9 or more factors, the default is main effects and 2-way interactions.
- Include blocks in the model
- If the optimal design has so few runs that you can collect the data under homogenous conditions, then you do not need blocks. If the optimal design has so many runs that you cannot collect all of the data under homogenous conditions, then include the blocks. Minitab enables this checkbox if the column that identifies the block of each experimental run in the candidate set has multiple values.