I am a doctoral student in clinical neuropsychology, and am in the process of creating z-unit weighted composite scores based on a battery of ability tests (i.e., attention/executive functions composite = Z scores for Trails A&B, Stroop, Digit span, RBANS coding, Symbol search). The scores will be used in a regression model involving a sample of 48 individuals with dementia and 32 normal healthy controls.
I am creating these scores using the recommendations on Jeromy Anglim's blog, but am looking for some additional solid references on the pros and cons of using composite scores. I would prefer to use factor analysis, however because I am working with a clinical sample (Alzheimer's disease) my sample size is too small.
- Can anyone recommend readings on the use and pros and cons of z weighted composite scores?
Best Answer
1. Which component tests to combine
2. How to combine chosen component tests
In the above, I'm not trying to say that unit-weighted sums of z-scores are the best way to form an ability composite. If anything, they are relatively simple approaches to the task of measuring and scaling multi-faceted ability constructs. I've merely tried to highlight why a researcher might adopt the approach.
A reference showing an example study
The following reference provides a case study of researchers discussing their rationale for combining component tests based on z-scores, and some of the issues that it entailed: