I want to include individual symptoms of a disorder to predict remission of the sum score of the disorder some weeks later (sum score = metric variable).
The individual symptoms are coded 0, 1, 2 and 3. They are not at all normally distributed, some of them are extremely skewed (e.g. 80% have 0 or 70% have 3). I want to treat them as ordinal, therefor.
Is there a way to do this in SPSS? Dummy coding would imply nominal, not ordered, and just entering them as predictors like they are makes me wonder whether SPSS treats them as metric.
If not, is there a way to do this in R? I'm new to R so ... don't really know much about it.