GLM repeated measure is a repetitive procedure to model dependent, or criterion variables, measured using analysis of variance. In GLM repeated measure, the independent variables may be categorical or continuous covariates. GLM repeated measure can be used to test the main effects within and between the subjects, interaction effects between factors, covariate effects and effects of interactions between covariates and between subject factors.
GLM repeated measures in SPSS is done by selecting “general linear model” from the “analyze” menu. From general linear model, select “repeated measures” and then perform “GLM repeated measures.”
There are certain terminologies in GLM repeated measure that will help in understanding GLM repeated measures in a much better manner. These terminologies are as follows:
- The within-subject factor in GLM repeated measure is the basic factor for the repeated measurements. This factor in GLM repeated measure carries certain levels. The within-subjects factor in GLM repeated measure will have as many levels as there are repetitions.
- Covariates in GLM repeated measures are quantitative independent variables.
- Bartlett’s test of sphericity test in GLM repeated measure tests whether or not the correlation matrix is an identity matrix. This will indicate if the factor model is inappropriate or not.
- Levene’s test in GLM repeated measure tests whether the variability is homogeneous or not.
- Residual Plot in GLM repeated measure shows the difference between the calculated and measured values of the dependent variables. A plot with excessive different trends will usually indicate an inappropriate model.
Assumptions
- Since it is a GLM repeated measure, the models assumed should be linear in nature.
- The dependent variables in GLM repeated measure should be assumed to follow a multivariate normal distribution.
- It should be assumed that the effects in GLM repeated measure should be fixed effects.
- The homogeneity of the variance is assumed in GLM repeated measures. This can be tested with the help of Levene’s test.
