# WHEN DO YOU USE A FACTORIAL DESIGN?

## Factorial designs are good preliminary experiments. This article will help you to understand when and how we can use the Factorial Design in DOE

WHEN DO YOU USE A FACTORIAL DESIGN?

Factorial designs are good preliminary experiments

A type of factorial design, known as the fractional factorial design, are often used to find the “vital few” significant factors out of a large group of potential factors.

This is also known as a screening experiment

¢Also used to determine curvature of the response surface

FULL FACTORIAL DESIGNS

Every combination of factor levels (i.e., every possible treatment) is measured.

2k design = k factors, each with 2 levels, 2k total runs

33 design = 3 factors, each with 3 levels, 33 = 27 total runs

Every factor effect can be estimated

Can include centre points, but not necessary

2k designs are the most popular

High Level (+1) and Low Level (-1)

Example: 22 design = 4 runs

Run Factor A Level Factor B Level

1 -1 -1

2 -1 +1

3 +1 -1

4 +1 +1

FULL FACTORIAL DESIGNS

Full factorials can also allow factors to have different number of levels

213241 = 4 factors total (sum of exponents) One factor has 2 levels, two have 3 levels, one has 4 levels Total of 2*3*3*4 = 72 runs

Ex. 2131 design = 6 runs

Run Factor A Level Factor B Level

1 1 1

2 1 2

3 1 3

4 2 1

5 2 2

6 2 3

For previous DOE Definition you can click

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