What is the calculation that you are using? The following KB might help provide some insight on how to solve these:
Thanks for your reply, Tracy. I read your link and it was very helpful but I haven't been able to solve my issue.
The calculation I'm trying to achieve is:
ZMeasure = [ Measure - Mean(Measure) ]/Std Dev(Measure)
where the 'Measure' is at a respondent level and the Mean & Standard Deviation are calculated across the sample of all respondents.