User Guide

Chapter 2

Main effects. Creates a main-effects term for each variable selected.

All 2-way. Creates all possible two-way interactions of the selected variables.

All 3-way. Creates all possible three-way interactions of the selected variables.

All 4-way. Creates all possible four-way interactions of the selected variables.

All 5-way. Creates all possible five-way interactions of the selected variables.

Sums of Squares

For the model, you can choose a type of sum of squares. Type III is the most commonly

used and is the default.

Type I. This method is also known as the hierarchical decomposition of the sum-of-

squares method. Each term is adjusted for only the term that precedes it in the model.

The Type I sum-of-squares method is commonly used for:

 A balanced ANOVA model in which any main effects are specified before any

first-order interaction effects, any first-order interaction effects are specified before

any second-order interaction effects, and so on.

 A polynomial regression model in which any lower-order terms are specified

before any higher-order terms.

 A purely nested model in which the first-specified effect is nested within the

second-specified effect, the second-specified effect is nested within the third, and

so on. (This form of nesting can be specified only by using syntax.)

Type II. This method calculates the sums of squares of an effect in the model adjusted

for all other “appropriate” effects. An appropriate effect is one that corresponds to all

effects that do not contain the effect being examined. The Type II sum-of-squares

method is commonly used for:

 A balanced ANOVA model.

 Any model that has main factor effects only.

 Any regression model.

 A purely nested design. (This form of nesting can be specified by using syntax.)