# Overview for Create Response Surface Design (Central Composite)

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 you estimate curvature. Usually, you use a central composite design after you have conducted a factorial or fractional factorial experiment and have identified the most important factors in your process. For more information, go to What are response surface designs, central composite designs, and Box-Behnken designs?.

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 Response Surface Design to analyze the data.

For example, an engineer wants to analyze the injection-molding process for a plastic part. First, the engineer performs a fractional factorial design, and identifies the important factors (temperature, pressure, cooling rate) and determines that curvature is present in the data. The engineer creates a central composite design to analyze the curvature and find the best factor settings.

This Minitab worksheet shows a portion of the central composite design. The engineer performs the experiment by collecting data using the order shown in the RunOrder column.

C1 C2 C3 C4 C5 C6 C7 C8
StdOrder RunOrder PtType Blocks Temperature Pressure Cooling rate
20 1 0 1 337.500 55 15.000
16 2 0 1 337.500 55 15.000
9 3 –1 1 316.478 55 15.000
13 4 –1 1 337.500 55 6.591
10 5 –1 1 358.22 55 15.000
18 6 0 1 337.500 55 15.000
14 7 –1 1 337.500 55 23.409

After collecting the data, the engineer enters the response data in an empty column in the worksheet and 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 > Response Surface > Create Response Surface Design

## When to use an alternate analysis

By using this site you agree to the use of cookies for analytics and personalized content.  Read our policy