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SPSS® 12.0 Command Syntax Reference

SPSS® 12.0 Command Syntax Reference

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GLM: Repeated Measures 681<br />

• Levels of the factors must be represented in the data by the dependent variables named on<br />

the GLM variable list.<br />

• The number of levels of each factor must be at least two. Enter an integer equal to or greater<br />

than 2 after each factor to indicate how many levels the factor has. Optionally, you can<br />

enclose the number of levels in parentheses.<br />

• Enter only the number of levels for within-subjects factors, not a range of values.<br />

• If more than one WSFACTOR subcommand is specified, only the last one is in effect.<br />

Contrasts for WSFACTOR<br />

The levels of a within-subjects factor are represented by different dependent variables.<br />

Therefore, contrasts between levels of such a factor compare these dependent variables.<br />

Specifying the type of contrast amounts to specifying a transformation to be performed on<br />

the dependent variables.<br />

• In testing the within-subjects effects, an orthonormal transformation is automatically<br />

performed on the dependent variables in a repeated measures analysis.<br />

• The contrast for each within-subjects factor is entered after the number of levels. If no<br />

contrast keyword is specified, POLYNOMIAL(1,2,3...) is the default. This contrast is used in<br />

comparing the levels of the within-subjects factors. Intrinsically orthogonal contrast types<br />

are recommended for within-subjects factors if you wish to examine each degree-offreedom<br />

test, provided compound symmetry is assumed within each within-subjects<br />

factor. Other orthogonal contrast types are DIFFERENCE and HELMERT.<br />

• If there are more than one within-subjects factors, the transformation matrix (M matrix)<br />

is computed as the Kronecker product of the matrices generated by the contrasts specified.<br />

• The transformation matrix (M matrix) generated by the specified contrasts can be<br />

displayed by using the keyword TEST(MMATRIX) on the subcommand PRINT.<br />

• The contrast types available for within-subjects factors are the same as those on the<br />

CONTRAST subcommand for between-subjects factors, described in “CONTRAST<br />

Subcommand” on p. 663 in GLM: Univariate.<br />

The following contrast types are available:<br />

DEVIATION Deviations from the grand mean. This is the default for between-subjects<br />

factors. Each level of the factor except one is compared to the grand mean.<br />

One category (by default the last) must be omitted so that the effects will<br />

be independent of one another. To omit a category other than the last, specify<br />

the number of the omitted category in parentheses after the keyword<br />

DEVIATION. For example,<br />

GLM Y1 Y2 Y3 BY GROUP<br />

/WSFACTOR = Y 3 DEVIATION (1)<br />

Deviation contrasts are not orthogonal.

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