Z Scores - Can I calculate an average on 2 Z-scores or should it be on raw data?

Hi there,

I have a series of Z-scores that are calculated twice for a single subject (they are similar but taken at 2 different times). But because the parameters are from the same subject we need to do an average. Therefore my question is, should I calculate average on a Z-Score or on the raw data that generated that z-score?

If you can give me any help it would be greatly appreciated.

Many thanks


TS Contributor
I would definitely take the average of the raw data. Adding z scores is not a defined operation imho.