Simple

Simple contrasts. Compares each level of a factor to the last. The general matrix form is

   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)

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:

(1/4   1/4   1/4  1/4)
(  1     0     0   -1)
(  0     1     0   -1)
(  0     0     1   -1)

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)

Suppose that factor has four categories. The resulting contrast matrix will be

(1/4   1/4   1/4  1/4)
(  1    -1     0    0)
(  0    -1     1    0)
(  0    -1     0    1)