User Guide

112
Appendix A
To omit a category other than the last, specify the number of the omitted category in
parentheses after the
DEVIATION keyword. For example, the following subcommand
obtains the deviations for the first and third categories and omits the second:
/CONTRAST(FACTOR)=DEVIATION(2)
Suppose that factor has three categories. The resulting contrast matrix will be
Simple
Simple contrasts. Compares each level of a factor to the last. The general matrix form is
where k is the number of categories for the independent variable. For example, the
simple contrasts for an independent variable with four categories are as follows:
To use another category instead of the last as a reference category, specify in parentheses
after the
SIMPLE keyword the sequence number of the reference category, which is not
necessarily the value associated with that category. For example, the following
CONTRAST subcommand obtains a contrast matrix that omits the second category:
/CONTRAST(FACTOR) = SIMPLE(2)
( 1/3 1/3 1/3 )
( 2/3 –1/3 –1/3 )
( –1/3 –1/3 2/3 )
mean (
1/k
1/k ... 1/k 1/k )
df(1) (
1
0... 0 –1 )
df(2) (
0
1... 0 –1 )
..
..
df(k–1) (
0
0... 1 –1 )
( 1/4 1/4 1/4 1/4 )
(1 0 0 –1 )
(0 1 0 –1 )
(0 0 1 –1 )