I received some old data that I am now supposed to analyze, however, deciding for an appropriate statistical test turned out to be a little hard for me, so I could Need your help!

The data are basically from a 2x2 factorial design with Pre- and Posttest measures. It is an Intervention study (intervention vs placebo) that was conducted in a group of patients as well as in a group of healthy controls, so in theory there are 4 different groups (patient+intervention, patient+placebo, control+intervention, control+placebo). Moreover, I have results from various questionnaires and neuropsychological tests from two different time points (pre- and post- intervention).

The Problem is, that the group sizes are rather small (around 15) and that most of the measures have different distributions for patients and controls (e.g. skewed for patients but normal for controls).

I am using SPSS, so I would prefer doing analyses with SPSS. My Questions are basically if there is any non-parametric equivalent to a Mixed Design? Or what test(s) do you suggest me to do? Any help is appreciated!

Thanks,

Kalu