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Use Create Response Surface Design (Central Composite) to create a designed experiment for 2−10 factors to model curvature in your data and identify factor settings that optimize the response. Central composite designs enable you to build on factorial or fractional factorial design by adding center points, augmented with axial points that let ...   

A central composite design is the most commonly used response surface designed experiment. Central composite designs are a factorial or fractional factorial design with center points, augmented with a group of axial points (also called star points) that let you estimate curvature.   

Choose Stat > DOE > Response Surface > Create Response Surface Design. Under Type of Design, select Central composite. From Number of continuous factors, select 3. Click Designs. Select the second design (full design with 20 runs and 2 blocks) in the white box, and then click OK. Click Results.   

A response surface design is used when you suspect curvature in the response. It allows you to add squared (or quadratic) terms to your model in order to analyze that curvature. A central composite design, one type of RSD, consists of: A central composite design with two factors is shown below.   

Find definitions and interpretation guidance for every statistic that is provided with the creation of a response surface central composite design.   

Summary of central composite designs. The table summarizes the designs generated by the central composite design commands. If the design has blocks, then the blocks are orthogonal.   

If the center point p-value is significant (i.e., less than alpha), then you can conclude that curvature exists and use response surface DOE—such as a central composite design—to analyze your data.   

Before you can analyze your data, you must use Create Response Surface Design (Central Composite), Create Response Surface Design (Box-Behnken) or Define Custom Response Surface Design to enter or define your design. You also need to have response data in the worksheet.   

A central composite design can always be separated into a factorial block and an axial point block. With three or more factors, the factorial block can also be split into two or more blocks. When you are creating a design, Minitab displays the appropriate choices.   

For more information on how Minitab blocks central composite designs, go to Blocks in a central composite design. Number of center points. Select the number of center points for the design. Center points are experimental runs where all of the factors are set midway between their low and high levels.