# Mixed linear model with repeated measures in SPSS

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.