I'm trying to run a mixed linear model analysis with SPSS. When I try to run the analysis, SPSS gives the following error message:
The levels of the repeated effect are not different for each observation within a repeated subject.
I am trying to use a mixed model because my data has some missing values and the GLM does not work (almost every participant has at least one missing value).
The test used a within subject design and this is how my data looks like:
Participant | Repetition | Axis | X | Y | Z | P_rate
participant is the ID of the test subject. Repetition represents the repeated observation, while Axis, X Y Z represent the particular combination of conditions for that observation (Axis has 3 levels, X,Y,Z have two each). There were two repetitions for each combination. So I have a total of 48 observations (2 x 3 x 2 x 2 x 2). P_rate is the dependent variable.
In the dialog window I use
Participant as my subject variable,
Repetition as my repeated variable and
Axis, X, Y, Z as my factors. However SPSS does not run the analysis because of that error.
What should I do in order for it to run the analysis correctly? I tried using an "Expectation Maximization" procedure to replace the missing values so that I could run a standard repeated measures ANOVA. It gives a significant difference for the Repetition parameter but just barely (p=0.049) so I wanted to use a mixed model to double check it.
Thanks in advance.