Having done poorly on a particular exam in a junior high school, 27 students decide to write the exam again to try and improve their mark. Results are given in the following table. Student n Average Standard deviation Attempt 1 (A, ) 27 51 3.7 Attempt 2 (A2) 27 55 4.9 Difference (d = A1 - A2) 27 -4.0 3.1 (a) Find an 80% confidence interval for the difference in mean scores between attempt 1 and attempt 2. ( Round your answers to 4 decimal places, if needed.) (b) Based on this confidence interval, can we conclude there is a difference in mean scores between attempt 1 and attempt 2? O Yes, since the interval contains 0. O Yes, since the interval is completely below 0. O No, since the interval is completely below 0. O No, since the interval contains 0