Editing Effect size (section)

==== Risk difference ====
The [[risk difference]] (RD), sometimes called absolute risk reduction, is simply the difference in risk (probability) of an event between two groups. It is a useful measure in experimental research, since RD tells you the extent to which an experimental interventions changes the probability of an event or outcome. Using the example above, the probabilities for those in the control group and treatment group passing is 2/3 (or 0.67) and 6/7 (or 0.86), respectively, and so the RD effect size is 0.86&nbsp;−&nbsp;0.67 = 0.19 (or 19%). RD is the superior measure for assessing effectiveness of interventions.<ref name="Stegenga2015"/>