An experiment was designed to estimate the mean difference in weight gain for pigs fed ration A as compared with those fed ration B. Eight pairs of pigs were used. The pigs within each pair were litter-mates. The rations were assigned at random to the two animals within each pair. The gains (in pounds) after 45 days are shown in the following table. Assuming weight gain is normal, find the 98%confidence interval estimate for the mean of the differences ?d, where d = ration A - ration B. (Give your answers correct to two decimal places.)
| Litter |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
| Ration A |
65 |
56 |
57 |
42 |
63 |
55 |
43 |
38 |
| Ration B |
55 |
52 |
53 |
38 |
62 |
52 |
37 |
31 |