A certain test preparation course is designed to help students improve their scores on the GRE exam. A mock exam is given at the beginning and end of the course to determine the effectiveness of the course. The following measurements are the net change in 6 students' scores on the exam after completing the course: 23,19,1,12,8,32 Using these data, construct a 95% confidence interval for the average net change in a student's score after completing the course. Assume the population is approximately normal.