Refer to the orange juice quality study, Exercise 9.14

(p. 484). Recall that a manufacturer that has developed a quantitative index of the "sweetness" of orange juice is investigating the relationship between the sweetness index and the amount of water soluble pectin in the orange juice it produces. The data for 24 production runs at a juice manufacturing plant are reproduced in the table on page 539.

a. Calculate Spearman's rank correlation coefficient between the sweetness index and the amount of pectin. Interpret the result.

b. Conduct a nonparametric test to determine whether there is a negative association between the sweetness index and the amount of pectin. Use a = .01.