An agency offers students preparation courses for a graduate school admissions test. As part of an experiment to evaluate the merits of the course, 12 students were chosen and divided into six pairs in such a way that the two members of any pair had similar academic records. Before taking the test, one member of each pair was assigned at random to take the preparation course, while the other member took no course.
The achievement test scores are contained in the Student Pair data file. Assuming that the differences in scores are normally distributed, find a 98% confidence interval for the difference in means scores between those who took the course and those who did not.