SPSS® 12.0 Command Syntax Reference

ONEWAY 1163
error, the t statistic, and the degrees of freedom and two-tailed probability of t for each variable.
Both pooled- and separate-variance estimates are displayed.
• A contrast coefficient must be specified or implied for every group defined for the independent
variable. If the number of contrast values is not equal to the number of groups,
the contrast test is not performed.
• The contrast coefficients for a set should sum to 0. If they do not, a warning is issued.
ONEWAY will still give an estimate of this contrast.
• Coefficients are assigned to groups defined by ascending values of the independent variable.
• The notation n*c can be used to indicate that coefficient c is repeated n times.
Example
ONEWAY V1 BY V2
/CONTRAST = -1 -1 1 1
/CONTRAST = -1 0 0 1
/CONTRAST = -1 0 .5 .5.
• V2 has four levels.
• The first CONTRAST subcommand contrasts the combination of the first two groups with
the combination of the last two groups.
• The second CONTRAST subcommand contrasts the first group with the last group.
• The third CONTRAST subcommand contrasts the first group with the combination of the
third and fourth groups.
Example
ONEWAY V1 BY V2
/CONTRAST = -1 1 2*0
/CONTRAST = -1 1 0 0
/CONTRAST = -1 1.
• The first two CONTRAST subcommands specify the same contrast coefficients for a fourgroup
analysis. The first group is contrasted with the second group in both cases.
• The first CONTRAST uses the n*c notation.
• The last CONTRAST does not work because only two coefficients are specified for four
groups.
POSTHOC Subcommand
POSTHOC produces post hoc tests for comparisons of all possible pairs of group means or multiple
comparisons. In contrast to a priori analyses specified on the CONTRAST subcommand,
post hoc analyses are usually not planned at the beginning of the study but are suggested by
the data in the course of the study.
• Twenty post hoc tests are available. Some detect homogeneity subsets among the groups
of means, some produce pairwise comparisons, and others perform both. POSTHOC
produces a Multiple Comparison table showing up to 10 test categories. Nonempty group
means are sorted in ascending order, with asterisks indicating significantly different