While the difference in their scores was statistically significant, the effect size (d = 0.4) reflected only a medium-size effect of item context on students' application of scientific explanations for natural selection.
The meta-analysis found a medium-size effect of increased REM eye-movement density in PTSD.
Values of 0.01 indicate small effects, values of 0.06 indicate medium size effects, and values of 0.14 are indicative of large effects [ 30].
The standard deviation in each cell is about 6, corresponding to a medium sized effect size of 0.36.
From a clinical perspective, effect sizes of 0.56 – 1.2 can be interpreted as large, while effect sizes of 0.33 – 0.55 are of medium size, and effects of 0 – 0.32 are small [ 45].
The size of effect of this difference at 6 weeks post-test was d = 0.58, and according to Cohen [ 51], this is a medium size of effect.
Post-hoc analyses were conducted to investigate the above findings that across the whole sample depression, anxiety and stress scale scores decreased by a medium size of effect from pre-test to 6 weeks post-test.
Mixed model analyses revealed a significant group by time interaction on ESA with a medium size of effect suggesting that the mobiletype program significantly increases ESA compared to an attention comparison.
A significant effect for time was found, F 2, 86.41) = 8.38, p <.001, with post-hoc analyses showing a significant whole sample decrease of 4.19 points between pre- and 6-week post-test, t 91.63) = 4.08, p <.001 and an above medium size of effect (d = 0.57), but no significant differences between pre- and post-test, nor post- and 6-week post-test.
In the absence of effect size guidelines, the medium effect size of 0.5 was adopted for the CRA and HADS.
