The article ??Effect of Refrigeration on the Potassium Bitartrate Stability and Composition of ItalianWines?? (A. Versari, D. Barbanti, et al., Italian Journal of Food Science, 2002:45??52) reports a study in which eight types of white wine had their tartaric acid concentration (in g/L) measured both before and after a cold stabilization process. The results are presented in the following table:

Find a 95% confidence interval for the mean difference ?between the tartaric acid concentrations before and after the cold stabilization process.

Wine Type Before After Difference 1 2.86 2.59 0.27 2 2.85 2.47 0.38 3 1.84 1.58 0.26 4 1.60 1.56 0.04 0.80 0.78 0.02 6 0.89 0.66 0.23 7 2.03 1.87 0.16 8 1.90 1.71 0.19