In Exercise 12.46 we used a one-way between-groups ANOVA to explore patients’ likelihood of wearing orthodontic appliances. The researchers compared students in primary school, junior high school, and high school. The data presented were hours spent wearing the appliance per day.

Primary school: 16, 13, 18 Junior high school: 8, 13, 14, 12 High school: 20, 15, 16, 18

a. Calculate the appropriate measure of effect size for this sample.

b. Based on Cohen’s conventions, is this a small, medium, or large effect size?

c. Why is it useful to have this information in addition to the results of a hypothesis test?