Definition

The design and analysis of experiments is a statistical methodology used to test and determine the effect of various process Inputs on the process output. It takes a structured and scientific approach by making purposeful changes on several Factors simultaneously and measuring the resulting changes in the output of interest, thus teasing out the relationship between them. This approach is much more powerful and efficient as compared to the One Factor At a Time (OFAT) approach.

DOE starts with the development of a formal plan for conducting an experiment, including the choices of the response to measure, Factors to test, levels of the Factors and their combinations to be employed. Proper planning is the most critical step in conducting a successful designed experiment. The experimental design includes the treatment combinations or ‘recipes’ to be performed in random order with a new set of experimental material each time.

Examples

A three-factor full factorial design might examine the impact of Air Conditioning (On/Off), Tire Pressure (Low/High), and Cruise Control (On/Off) on a vehicle’s fuel efficiency. By testing all combinations of high and low levels for each factor, practitioners can uncover which settings have the greatest influence on miles per gallon, and whether any interactions exist between the factors (e.g., cruise control being more effective when tire pressure is high).

Application

1. Define the objective of the experiment (e.g., optimize yield, reduce variation).
2. Identify key input factors and determine the levels to test (e.g., high vs. low).
3. Select an appropriate experimental design (e.g., full factorial, fractional factorial).
4. Randomize the order of runs and collect output data under each condition.
5. Analyze the results using statistical methods to identify significant factors and interactions.
6. Validate findings with a confirmation run, then implement the improvements in the process.

See Also

Hypothesis Test
Regression Analysis
Factorial Design
Response Surface Methods

External Links

Characteristics of a Well-Designed Experiment - https://www.moresteam.com/resources/blogs/characteristics-well-designed-experiment Introduction to DOE in EngineRoom - https://www.moresteam.com/help/engineroom/doe-introduction Design of Experiments - https://en.wikipedia.org/wiki/Design_of_experiments Quick History on the Design of Experiments - https://online.stat.psu.edu/stat503/lesson/1/1.1 Getting Started with Design of Experiments: Part 1 - https://www.moresteam.com/resources/webcasts/getting-started-with-doe Getting Started with Design of Experiments: Part 2 - https://www.moresteam.com/resources/webcasts/getting-started-with-doe-part2 Design of Experiments in MoreSteam Toolbox - https://www.moresteam.com/toolbox/design-of-experiments