The manager of CORAIL wants to introduce a new railway management system. The manager believes that the new system will make the arrival time of the subway more constant, and to prove this, he/she will randomly select the arrival interval of the subway at Suwon Station to verify that his/her claim is correct. Answer the questions below when the data is shown below.

8 8.9 8.2 8.5 7.7 7.5 6.9 8.4

7.2 8.2 6.9 7 8.6 9 8.7 6.5

A. Under the existing railway management system, the variance of the arrival interval is 1min^2. Can we say that the new system has made the interval between arrivals of subways more constant? ( = 0.05)

B. What is the confidence interval for the variance of the subway arrival interval under the new system?