The Princeton review claims that students who take their course improve their GRE scores, on average, by 210 points. Researchers wonder if studying on your own will lead to a different average gain. They select five students from their university and give them a practice test before and after two months of self-study. This group improved their GRE score, on average, by 162 points with a standard deviation of 9 points. What test should the researcher use to determine whether or not this is a meaningful difference