Contents
What are covariates in repeated measures ANOVA?
The repeated measures ANCOVA compares means across one or more variables that are based on repeated observations while controlling for a confounding variable. Again, a repeated measures ANCOVA has at least one dependent variable and one covariate, with the dependent variable containing more than one observation.
How do you interpret ANCOVA in SPSS?
The steps for interpreting the SPSS output for ANCOVA
- Look in the Levene’s Test of Equality of Error Variances, under the Sig.
- Look in the Tests of Between-Subjects Effects, under the Sig.
- Look at the p-value associated with the “grouping” or categorical predictor variable.
Can you control for covariates in an ANOVA?
The one-way ANCOVA (analysis of covariance) can be thought of as an extension of the one-way ANOVA to incorporate a covariate. However, whereas the ANOVA looks for differences in the group means, the ANCOVA looks for differences in adjusted means (i.e., adjusted for the covariate).
How can I do repeated measures ANOVA with covariates in?
SPSS provides several ways to analyze repeated measures ANOVA that include covariates. This FAQ page will look at ways of analyzing data in either wide form, i.e., all of the repeated measures for a subject are in one row of the data, or in long form where each of the repeated values are found on a separate row of the data.
When to use pretest as a covariate in repeated measures?
In a repeated measures ANOVA with a pretest and one or more posttests, the critical indication of a differential effect of the grouping factor is the presence of a group*time interaction. It usually does not matter so much that one group starts out higher (or lower) than another at pretest.
How are time-varying covariates different from time invariant covariations?
With time-invariant covariates there is just one value that is used for all the repeated observations for a given subject. Time-varying covariates, on the other hand, can take on a different value for each of the repeated observations.
Is there a main effect for the covariate?
There is no main effect for the covariate in the within-subjects portion of the analysis. There is only an interaction with the within-subjects factor. A significant result implies that the change over trials depends upon the level of the covariate.