a sample of n = high school students took the SAT before and after a special training course. For each student, the difference between the first score and the second score was measured and the results showed that their SAT scores averaged MD = 18 points higher after the course with SS = 6000. On the basis of this sample, can you conclude that there was a significant difference after taking the training course? What do you conclude? Use a two-tailed test at the .05 level of significance.