A chemistry teacher wishes to test whether using handheld models is beneficial when learning about molecules. From prior experience, the teacher knows to expect average performance on the molecular portion of the exam to be 0.61 with a standard deviation of 0.15 when handheld models are not available. After teaching a lesson about molecules to a sample of 34 students who used handheld models, the teacher measured the average performance as 0.67, and calculated an effect size measure of d = 0.40. Select the correct interpretation of the effect size