Modeling and Multivariate Methods - SAS

40 Introduction to the Fit Model Platform Chapter 2
Construct Model Effects
Cross
The Cross button creates interaction or polynomial effects. Select two or more variables in the Select
Columns list and click Cross.
See the appendix “Statistical Details” on page 651 in the “Statistical Details” appendix, for a discussion of
how crossed effects are parameterized and coded.
Note: JMP allows up to ten terms to be combined as crossed and nested.
Nest
Explanation of Crossed Effects
As an illustration of what the Cross button does, consider a cell phone manufacturer that wants to
experiment to determine the effect of two factors: plastic types and rubber types. The manufacturer is
examining two types of plastics (p1 and p2) and two types of rubber (r1 and r2). In the experiments, both
levels of plastic are combined with both levels of rubber, producing the following combinations:
• p1*r1
• p1*r2
• p2*r1
• p2*r2
Since there are no restrictions on combining the levels of plastic and rubber, you can add a crossed term to
your model. In the Construct Model Effects panel, you would add the following effects: P, R, P*R.
The Nest button creates nested effects. If the levels of one effect (B) occur only within a single level of
another effect (A), then B is said to be nested within A. A is called the outside effect and B is called the
inside effect. The notation B[A] is read as B within A.
For example, in the Fit Model launch window, proceed as follows:
1. Add both A and B to the Construct Model Effects panel.
2. In the Construct Model Effects panel, click on B.
3. In the Select Columns list, click on A.
4. Click Nest.
Note: The nesting terms must be specified in order from outer to inner. For example, if B is nested within
A, and C is nested within B, then the model is specified as: A, B[A], C[B,A]. JMP allows up to ten terms to
be combined as crossed and nested.