Question: (PART 1 - I already answered)

A wireless communication company is considering switching from a per-minute charge to a flat monthly fee for unlimited service. It anticipates that this will result in greater usage and would like to estimate the change in the average number of minutes per month per customer resulting from the new plan. To do this, it offers 850 customers the flat-fee plan for one month and tracks their usage. It also tracks a control group of 700 customers under the old plan. Among the 850 test customers, it finds an average usage of 227 minutes and a sample standard deviation of 135 minutes; in the control group, the corresponding values are 163 and 85. Find a 95% confidence interval of the average number of minutes per month difference under the two plans. ---> Answer: 64 11.04

PART 2 - Need answer to:

Continuation of Problem 1: Is it statistically significant at 5% and 10% level that the average number of minutes per month is different under the two plans?

A. No, no

B. No, yes

C. Yes, no

D. Yes, yes