Interpret the key results for Create Definitive Screening Design

Complete the following steps to examine the design that you created.

Step 1: Examine the design properties

Use the summary of the design to examine the key design properties. Most properties of the design match selections that you made for the base design during design creation. The total runs are greater than the base runs when the design has multiple replicates. Each replicate adds runs equal to the number of runs in the base design.

Key output: Design summary

In these results, the base design has 17 runs. The total number of runs is 34 because the design has 2 replicates. Because all of the factors are continuous, the number of center points equals the number of replicates.

Design Summary

Base runs:17Total runs:34
Base blocks:1Total blocks:1
Center points:2   

Step 2: Collect experimental data

When you create your design, Minitab stores the design information in the worksheet. Minitab includes columns for standard order (StdOrder), run order (RunOrder), point type (PtType), blocks (Blocks), and a column for each factor. For more information, go to How Minitab stores design information in the worksheet.

You can use the worksheet to guide your experiment because it lists the factor settings for each experimental run and, if you randomized the design, the order in which you should perform the runs. If you didn't randomize the design, you can do that with Modify Design. Before you perform the experiment, you should name one or more columns in the worksheet for the response data. After you enter the response data, you can use Analyze Screening Design to analyze the design.

For example, this worksheet shows a design with 4 factors, Temp, Time, Material, and Pressure. The first row in the worksheet contains the first experimental run, where temperature is set to 100, the time is set to 5, formula 1 is used, and the pressure is set to 75. After this run is performed, the measurement for strength can be entered into the worksheet.

C1 C2 C3 C4 C5 C6 C7-T C8 C9
StdOrder RunOrder PtType Blocks Temp Time Material Pressure Strength
6 1 1 1 100 5 Formula1 75  
2 2 1 1 200 10 Formula2 150  
9 3 0 1 150 7.5 Formula2 112.5  
5 4 1 1 200 10 Formula1 75  
1 5 1 1 200 5 Formula1 150  

Before you perform the experiment, there are several activities you can do to help ensure that your experiment is successful.
  • Document procedures for the experiment and train the individuals who are involved in the experiment.
  • Validate the measurement system to ensure that it is accurate.
  • Review the factor level combinations to make sure they are all feasible.
  • Perform trial runs to check materials, equipment, and procedures.

For more information, go to Checklist of pre-experiment activities.