If I have a sample of 137 individuals with three assessment results (first, 1YR follow-up and 2-Yr follow-up), can I calculate the Reliable Change Index (RCI) for the group or do I have to calculate it for each individual and then say what proportion of individuals had a significant result?

For significance, I assume I would use the threshold of t>=1.96 or t<=-1.96 for significance?

Also, I'm wondering how to do this in SPSS, but I will also ask in that forum.