What is a designed experiment?

A designed experiment is a series of runs, or tests, in which you purposefully make changes to input variables at the same time and observe the responses. In industry, designed experiments can be used to systematically investigate the process or product variables that affect product quality. After you identify the process conditions and product components that affect product quality, you can direct improvement efforts to enhance a product's manufacturability, reliability, quality, and field performance.

For example, you work at an offset printing company where some customers have complained of pages coming unattached from their books' bindings. You suspect several factors: glue temperature, paper type, and cooling time. You want to determine which factors, or combinations of factors, significantly affect the effectiveness of your company's binding technique. When you create a designed experiment, Minitab automatically randomizes the run order of the design and displays the design in your worksheet. The run order is the ordered sequence of factor combinations. You can use the worksheet to record your responses when you do your experiment.

Minitab offers the following designed experiments:

Screening designs
Factorial designs
Response surface designs
Mixture designs
Taguchi designs

Designed experiments are often done in four phases: planning, screening (also called process characterization), optimization, and verification.

Note

Our intent is to provide only a brief introduction to the design of experiments. There are many resources that provide a thorough treatment of these methods.