Multiple Comparison Procedures - Analysis of Variance Designs - page 137

Ta b l e 7 . 3 . Preset contrasts in SPSS dialog windows

Reference group

Contrast Dialog Pairwise/ Orthogonal

name window nonpairwise contrasts Level Role Description

First/last ∗

Deviation Contrasts Nonpairwise No Omitted Each group except the reference group is compared to

the grand mean (which includes the reference group
in the calculation).

Difference Contrasts Nonpairwise Yes Not applicable Not applicable Each group except the lowest is compared to the average

of the groups coded with lower values (e.g., Level 4 is
compared to the average of Levels 1, 2, and 3). This is
the mirror image of Helmert contrasts.

Dunnett Post Hoc Pairwise No First/last ∗ Focus Each group is separately compared to the reference

group. It can be run two-tailed or directional. This is
the same strategy that is used by Simple contrasts.

Helmert Contrasts Nonpairwise Yes Not applicable Not applicable Each group except the highest is compared to the

average of the groups coded with higher values (e.g.,
Level 1 is compared to the average of Levels 2, 3, 4,
and 5). This is the mirror image of Difference
contrasts.

Repeated Contrasts Pairwise No Not applicable Not applicable Each group is compared to the adjacent group (Level 1

is compared to Level 2, Level 2 is compared to Level
3,andsoon).

First/last ∗ Simple Contrasts Pairwise No Focus Each group is separately compared to the reference

group. This is the same strategy that is used by the
Dunnett test; it has about the same amount of power
a directional Dunnett test.

∗ Using syntax, any group can be used as the reference.