JMP for Mixed Models

Chapter 4Multiple Random Effects

In this chapter, we investigate experiments with more than one random effect. There are many different ways this can occur, and an exhaustive list would be nearly impossible to compile. We will focus on a few of the most common. We will also explore the modeling of random effects a bit deeper, encountering an example with a negative estimated block variance.

4.1 Motivating Examples

Fabric Shrinkage — A fabric manufacturer needs to test four new materials to be used in permanent press garments. The heat chamber used to test fabrics has four positions. Each fabric should be tested under each position, and due to time constraints, the manufacturer is limited to four runs. Fabric shrinkage is the response of interest. ...