Final answer:
a. The length of the confidence interval is 7.2. b. The confidence interval is (48.7, 55.9) if the sample mean is 52.3. c. The graph shows the sample mean with upper and lower bounds.
Step-by-step explanation:
a. The length of the confidence interval is 7.2.
b. To obtain the confidence interval, we add and subtract the margin of error from the sample mean. Therefore, the confidence interval is (48.7, 55.9).
c. The graph illustrating the results would show a horizontal line at the sample mean (52.3) with two vertical lines representing the upper and lower bounds of the confidence interval.