Tools for Those Who Summarize the Evidence Base
We are running a meta-analysis looking at the association between psychopathy and impulsivity and some studies report both group comparisons (psychopaths vs non-psychopaths) and correlations between psychopathy scores and impulsivity.
What do you do in those instances? Do you calculate the two effect sizes (i.e., from the group comparison and from the correlation) and average them to obtain an overall effect size? What would you recommend when the correlation is run across the two groups or just in the psychopathy group?