I am a PhD student and am conducting a literature review on musculoskeletal physiotherapy and am struggling to get guidance on this subject as most health researchers conduct meta-analyses of intervention effects/ effectiveness and not of correlations.
I am looking at the predictors of attendance and adherence to treatment recommendations in musculoskeletal physiotherapy.
- The dependent variable is adherence operationalised into 4 aspects - attendance, in clinic adherence, home exercise adherence and long term adherence.
- The independent variables range from nominal ones like gender, ordinal like socio economic status as well as interval ratio measurements.
Having looked at literature and discussed with a couple of people, I feel that correlation 'r' is the effect size that we would need to use, and for nominal or ordinal data, we can use 2x2 contigency tables, calculate t or chi square and then convert it to 'r'. Then we apply an 'r' to 'z' transformation to combine results and then reconvert it to 'r' for interpretation.
Is this the right approach? What other factors should be considered?
Another issue is that I am taking several different diseases like neck pain, low back pain, ankle injury etc. Is it too heterogeneous to conduct meta analysis even though they have a common symptomatic presentation?