I will be conducting a meta-analysis that compares post-treatment changes in depression between the control and intervention groups. I have the Mean, SD, and N for depression at both time-points. Since different studies used measures to assess depression, I was planning to convert the change scores into z-scores to decrease heterogeneity.
I understand the standard z-score formula is z = (x - meanx) / SDpool, where x is the pre - post-treatment change, but I'm not sure about the other two variables. Is meanx the mean change, and SDpool the SD across all change scores (including both control and intervention values) for all studies?
Any help would be appreciated, thank you!
I understand the standard z-score formula is z = (x - meanx) / SDpool, where x is the pre - post-treatment change, but I'm not sure about the other two variables. Is meanx the mean change, and SDpool the SD across all change scores (including both control and intervention values) for all studies?
Any help would be appreciated, thank you!