132 Sentence complexity study. Applied Psycholinguistics (June 1998) conducted a study of language skills of low-income children. Each in a sample of 65 low-income children was administered the Communicative Development Inventory

(CDI) exam. The sentence complexity scores had a mean of 62 and a standard deviation of 8.91.

a. Construct a 90% confidence interval for the mean sentence complexity score of all low-income children.

b. Interpret the interval you found in part a in the words of the problem.

c. Suppose we know that the true mean sentence complexity score of middle-income children is 15.55. Is there evidence that the true mean for low-income children differs from 15.55? Explain.