is it appropriate to take the absolute value of a correlation coefficient to include in analyses? I am planning a meta-analysis and some of the hypothesized outcome variables might have a negative relationship. To include in one model, would it be okay to use the absolute value of the correlations to be consistent with other coefficients?
Edit: to clarify, I want to include correlation coefficients in a random-effects model for meta-analysis. If the majority of the correlations are positive, could I use the absolute values of the negative correlations if such correlations would have been positive had one of the measures been reverse scored?