Random-Effects Model (k = 21; tau^2 estimator: REML)

tau^2 (estimated amount of total heterogeneity): 187.0183 (SE = 133.7620)
tau (square root of estimated tau^2 value):      13.6755
I^2 (total heterogeneity / total variability):   46.42%
H^2 (total variability / sampling variability):  1.87

Test for Heterogeneity: 
Q(df = 20) = 35.4051, p-val = 0.0180

Model Results:

estimate       se     zval     pval    ci.lb    ci.ub          
-48.7085   4.7248 -10.3091   <.0001 -57.9689 -39.4480      *** 

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Signif. codes:  0 *** 0.001 ** 0.01 * 0.05 . 0.1   1 