A certain test preparation course is designed to help students improve their scores on the GRE cam. A mock exam is pen at the beginning and end of the course to determine the effectiveness of the course. The following measurements are the net change in 7 students' scores on the cum after completing the course 15, 12-3, 10, 18,0,13 Using these data, construct a 80 % confidence interval for the average net change in a students score after completing the course Assume the population is approximately normal, CopyData Step 3 of 4: Find the critical value that should be used in constructing the confidence interval Round your answer to three decimal places Tables Prev Keypad Keyboard Shortcuts Next