SPSS® 12.0 Command Syntax Reference

678 GLM: Repeated Measures
Overview
This section discusses the subcommands that are used in repeated measures designs, in
which the dependent variables represent measurements of the same variable (or variables)
taken repeatedly. This section does not contain information on all of the subcommands that
you will need to specify the design. For some subcommands or keywords not covered here,
such as DESIGN, see GLM: Univariate. For information on optional output and the multivariate
significance tests available, see GLM: Multivariate.
• In a simple repeated measures analysis, all dependent variables represent different
measurements of the same variable for different values (or levels) of a within-subjects
factor. Between-subjects factors and covariates can also be included in the model, just as
in analyses not involving repeated measures.
• A within-subjects factor is simply a factor that distinguishes measurements made on the
same subject or case, rather than distinguishing different subjects or cases.
• GLM permits more complex analyses, in which the dependent variables represent levels
of two or more within-subjects factors.
• GLM also permits analyses in which the dependent variables represent measurements of
several variables for the different levels of the within-subjects factors. These are known
as doubly multivariate designs.
• A repeated measures analysis includes a within-subjects design describing the model to
be tested with the within-subjects factors, as well as the usual between-subjects design
describing the effects to be tested with between-subjects factors. The default for the
within-subjects factors design is a full factorial model which includes the main withinsubjects
factor effects and all their interaction effects.
• If a custom hypothesis test is required (defined by the CONTRAST, LMATRIX, or KMATRIX
subcommands), the default transformation matrix (M matrix) is taken to be the average
transformation matrix, which can be displayed by using the keyword TEST(MMATRIX) on
the PRINT subcommand. The default contrast result matrix (K matrix) is the zero matrix.
• If the contrast coefficient matrix (L matrix) is not specified, but a custom hypothesis test
is required by the MMATRIX or the KMATRIX subcommand, the contrast coefficient matrix
(L matrix) is taken to be the L matrix which corresponds to the estimable function for the
intercept in the between-subjects model. This matrix can be displayed by using the
keyword TEST(LMATRIX) on the PRINT subcommand.
Basic Specification
• The basic specification is a variable list followed by the WSFACTOR subcommand.
• Whenever WSFACTOR is specified, GLM performs special repeated measures processing.
The multivariate and univariate tests are provided. In addition, for any within-subjects
effect involving more than one transformed variable, the Mauchly test of sphericity is
displayed to test the assumption that the covariance matrix of the transformed variables
is constant on the diagonal and zero off the diagonal. The Greenhouse-Geisser epsilon
and the Huynh-Feldt epsilon are also displayed for use in correcting the significance tests
in the event that the assumption of sphericity is violated.