Repeated

Compares adjacent levels of an independent variable. The general matrix form is

   
   mean (1/k  1/k  1/k  ...  1/k  1/k)
  df(1) (  1   -1    0  ...    0    0)
  df(2) (  0    1   -1  ...    0    0)
      .         .
      .         .
df(k-1) (  0    0    0  ...    1   -1)

where k is the number of categories for the independent variable. For example, the repeated contrasts for an independent variable with four categories are as follows:

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

These contrasts are useful in profile analysis and wherever difference scores are needed.