The 1967 Age Discrimination in Employment Act

(ADEA) made it illegal to discriminate against workers 40 years of age and older. Opponents of the law argue that there are sound economic reasons why employers would not want to hire and train workers who are very close to retirement. They also argue that people's abilities tend to deteriorate with age. In fact, Forbes (Dec. 13,1999) reported that 25-year-olds did significantly better than 60-year-olds on the Wechsler Adult Intelligence Scale, the most popular IQ test.

The data on p. 268 are raw test scores (i.e., not the familiar normalized IQ scores) for a sample of 36 25-

year-olds and 36 60-year-olds.

a. Estimate the mean raw test score for all 25-year-olds using a 95% confidence interval. Give a practical interpretation of the confidence interval.

b. What assumption(s) must hold for the method of estimation used in part a to bc appropriate'?

c. The STATISTIX printout above provides an analysis of the saniplc raw test scores ol 60-year-olds. Find a 95% confidence interval for the mean raw score of all 60-year-olds and interpret your result. [Note: In Chaptcr 9 we will present a method for directly comparing the means ol 25-year-olds and 60-year-olds.]