SPSS® 12.0 Command Syntax Reference

866 MANOVA: Univariate
• You can obtain the unweighted mean by specifying the full factorial model, excluding
those terms contained by an effect, and prefixing the effect whose mean is to be found by
MUPLUS.
Effects of Continuous Variables
Usually you name factors but not covariates on the DESIGN subcommand. The linear effects
of covariates are removed from the dependent variable before the design is tested. However,
the design can include variables measured at the interval level and originally named as covariates
or as additional dependent variables.
• Continuous variables on a DESIGN subcommand must be named as dependents or covariates
on the MANOVA variable list.
• Before you can name a continuous variable on a DESIGN subcommand, you must supply an
ANALYSIS subcommand that does not name the variable. This excludes it from the analysis
as a dependent variable or covariate and makes it eligible for inclusion on DESIGN.
• More than one continuous variable can be pooled into a single effect (provided that they
are all excluded on an ANALYSIS subcommand) with the keyword POOL(varlist). For a single
continuous variable, POOL(VAR) is equivalent to VAR.
• The TO convention in the variable list for POOL refers to the order of continuous variables
(dependent variables and covariates) on the original MANOVA variable list, which is not
necessarily their order on the working data file. This is the only allowable use of the keyword
TO on a DESIGN subcommand.
• You can specify interaction terms between factors and continuous variables. If FAC is a
factor and COV is a covariate that has been omitted from an ANALYSIS subcommand, FAC
BY COV is a valid specification on a DESIGN statement.
• You cannot specify an interaction between two continuous variables. Use the COMPUTE
command to create a variable representing the interaction prior to MANOVA.
Example
* This example tests whether the regression of the dependent
variable Y on the two variables X1 and X2 is the same across
all the categories of the factors AGE and TREATMNT.
MANOVA Y BY AGE(1,5) TREATMNT(1,3) WITH X1, X2
/ANALYSIS = Y
/DESIGN = POOL(X1,X2),
AGE, TREATMNT, AGE BY TREATMNT,
POOL(X1,X2) BY AGE + POOL(X1,X2) BY TREATMNT
+ POOL(X1,X2) BY AGE BY TREATMNT.
• ANALYSIS excludes X1 and X2 from the standard treatment of covariates, so that they can
be used in the design.
• DESIGN includes five terms. POOL(X1,X2), the overall regression of the dependent
variable on X1 and X2, is entered first, followed by the two factors and their interaction.
• The last term is the test for equal regressions. It consists of three factor-by-continuousvariable
interactions pooled together. POOL(X1,X2) BY AGE is the interaction between
AGE and the combined effect of the continuous variables X1 and X2. It is combined