Hello, i'm trying to calculate an Index of Cognitive Reserve, i have an instrument and a few proxy variables, so i want to get 1 number (or variable) that includes a combination of all the data. So, i have a few ideas which include: a single average of all the variables or doing a factor analysis. But right now, i want to read some papers with methodology regarding How to calculate or select the best method for the calculations according the type of data.

Thanks a lot on any feedback you can give.

Regards