An experiment was designed to estimate the mean difference in weight gain for pigs

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 littermates. The rations were assigned at random to the two animals within each pair. The gains (in pounds) after 45 days are shown below:

Assuming weight gain is normal, find the 95% confidence interval estimate for the mean of the differences μd where d= ration A – ration B.