It is believed that animals living in northern regions have shorter appendages than animals living in southern regions. Random samples of birds were selected from each group and wing lengths for birds (in millimeters) were measured. The following table gives summary statistics.
| Region | n | Average | Standard deviation |
| Northern (N) | 30 | 112.5 | 1.5 |
| Southern (S) | 30 | 113.0 | 3.2 |
| Difference (d = N - S) | 30 | -0.5 | 1.4 |
(a) Find a 98% confidence interval for the mean difference of wing lengths of birds between the northern regions and the southern regions. (Round your answers to 4 decimal places, if needed.)
(, )
(b) Based on this confidence interval, is there enough evidence to support the belief?
Yes, since the interval contains 0.
No, since the interval contains 0.
No, since the interval is completely below 0.
Yes, since the interval is completely below 0.