On the other hand, reductions in substance use generally represented small effect sizes.
Nevertheless, all these differences only represent small effects [ 36].
The actual d-effect sizes of 0.19, 0.28 and 0.23 represent small effects.
Cohen [ 32] provides a general rule-of-thumb for the interpretation of such effect size estimates: effect sizes of about 0.20 represent small effects, those of about 0.50 represent moderate effects, and those greater than about 0.80 represent large effects.
However, Pearson's effect sizes (r) for these differences were all small, as interpreted by Cohen where r < 0.30 represents small effects, r = 0.30 0.50 moderate effects and r > 0.50 large effects [ 50].
Correlation coefficients (r) or partial eta-squared (η p 2 ) are reported indicating the effect sizes (r < .10 and η p 2 <.05 representing small effects, r < .30 and η p 2 around.10 representing medium effects, and r > .50 and η > .20 representing large effects; Cohen, 1973, 1988).
According to Cohens' guidelines [ 27], these effect sizes should be interpreted with ds around.20 representing small effect sizes, ds of about.50 moderate effect sizes and ds above.80 large effect sizes.
Scoring outside the normal range for internalizing and externalizing child behavior symptoms independently contributed to lower MCS scores (-1.9 and -2.8, both with wide confidence intervals), with the change representing small effect sizes of 0.18 and 0.27.
The range of effect sizes represent small to moderate effect sizes as defined by Cohen [ 22].
Effect sizes were 11% for physical well-being and self-esteem, 7% for the total QoL score and school, and 1% for emotional wellbeing, friends and family, representing small to medium effects.
