Improving the Understanding of Statistical Significance

Abstract

The use of effect size as an approach to improve the communication of the clinical or policy significance of a statistically significnat t-test was investigated with three groups of statistics students Presenting only the values of t, df, and probability resulted in an overestimation of the difference between the means of a control group and the treatment group Including a statement about effect size and the percentile rank of the mean of the treatment group with respect to the control group, improved the students' accuracy (p < .05). Providing effect size information enabled undergraduates to nearly match the accuracy of graduate students who were not given effect size information.