In addition to reporting statistical
significance, it is highly recommended that effect size or some measure of
strength of effect be reported. The current Results section reports a basic form
of effect size called Cohen’s *d*. The general conventions for the labeling
of effect sizes are as follows: .2 is small, .5 is medium, and .8 is large.
Cohen’s *d* is easily calculated by hand and the components of this
calculation can be found on the __SPSS Output Analysis__. Essentially,
Cohen’s *d* is equal to the mean difference divided by the standard
deviation. In the case of a between-subjects design, the analysis will report
one standard deviation value for each of the two groups. Before dividing the
mean difference by a standard deviation value, the weighted average for these
two should be calculated and used as the denominator.