A certain test preparation course is designed to help students improve their scores on the USMLE 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: ll]. 18.15.14, 4.14 Using these data. construct a 30 5% condence interval for the average net change in a student's score after completing the course. Assume the population is approximatelyr normal. Copy Data Step 3 of 4: Find the critical value that should be used in constructing the confidence interval. Round your answer to three decimal places