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Optimal Design

Fold Design Window

Optimal Design Window

The Optimal Design window is used to select test runs from a design table in order to minimize the estimation uncertainty of the coefficients in a given regression model. It takes into account a) the specific effects that are under investigation, b) limitations on the number runs that can be performed and c) constraints on the factor level combinations that can be used during the experiment. The ReliaWiki resource portal provides more information on optimal custom designs at: http://www.reliawiki.org/index.php/Optimal_Custom_Designs.

To access the Optimal Design window, build a design and then choose Data > Design > Optimal Design.

The window includes two tabs discussed next.

Design Settings Tab

This tab is used to specify the method that will be used to create the design. Follow the steps outlined below to enter the settings.

The first section in this area concerns the random elements that are used in the generation of the design.

      • Select the Use Seed check box if you would like to set a consistent starting point from which the random numbers will be generated. Using the same seed value and keeping all other settings the same will allow you to replicate the resulting design.

      • Specify the Number of random initial runs that will be used. The software uses each random initial run to generate a design (using the algorithm you specify next), and then returns the best design that was found. Using more initial runs may produce a better design, but it will also increase the time required to generate the final design.

The second section is used to select the algorithm that will be used to generate the design. Three algorithms are available.

 

How likely to produce the optimal design?

How fast?

Federov's Method

Most likely

Slowest

Modified Federov's Method

Somewhat likely

Somewhat fast

K-Exchange Method

Least likely

Fastest

 

Candidate Runs Tab

This tab is used to select which runs will be considered in the final design. By default, the table on the Candidate Runs tab shows all the runs used in the current design. If desired, you can modify the factor levels in any of the runs.

Follow the steps outlined next to choose the runs to consider and, if desired, add/remove runs.

 

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