When a difference is statistically significant, it does not necessarily mean that it is big, important, or helpful in decision-making. It simply means you can be confident that there is a difference. Let’s say, for example, that you evaluate the effect of an EE activity on student knowledge using pre and posttests. The mean score on the pretest was 83 out of 100 while the mean score on the posttest was 84. Although you find that the difference in scores is statistically significant (because of a large sample size), the difference is very slight, suggesting that the program did not lead to a meaningful increase in student knowledge.