Interactions

A interaction is when the result is not the sum of two factors. With an interaction it can occur that the result of the to factors is lower or higher as the sum of the result.
When using an Orthogonal array interactions are not included. The interactions have to be included in the array this can be calculated with Develve.
Be careful with adding interactions in a design:

• A interaction is not a common thing
• Adding interactions will increase the array size especially in a 3 level array (2 extra test runs)
• If it is not logic that an interaction between factors do not include it

Interaction with the typical crossing line	No interaction

For the interaction Dialog go to DOE=>Interactions

This Dialog is for selecting interaction that needs to be calculated in a Design of Experiment.

Example

Data file

The Matrix indicates that Column C (pink means error) can not be used because that it is be used by the interaction. A bigger orthogonal matrix is needed. The indication of errors in the array is only been displayed when the check-box Check is on in the statistical mode plane.

With a bigger matrix it is possible to calculate the interaction.



The not used Columns can be removed. This is the result with measure data.

There is a interaction between Size and Weight and no interaction between Size and Color.

Adding a extra interaction between D and G the interaction dialogue will indicate that there is an error because both interactions interact with each other.

External links

• http://www.itl.nist.gov/div898/handbook/pri/section6/pri623.htm
• http://en.wikipedia.org/wiki/Interaction_%28statistics%29