Detecting Alzheimer’s disease at an early age. Refer to the Neuropsychology (Jan. 2007) study of whether the cognitive effects of Alzheimer’s disease can be detected at an early age, Exercise 13.17 (p. 808). Recall that a particular strand of DNA was classified into one of three genotypes:

E4 +>E4 +, E4 +>E4 - , and E4 - >E4 - . In addition to a sample of 2,097 young adults (20–24 years), two other age groups were studied: a sample of 2,182 middle-aged adults

(40–44 years) and a sample of 2,281 elderly adults (60–64 years). The accompanying table gives a breakdown of the number of adults with the three genotypes in each age category for the total sample of 6,560 adults. The researchers concluded that “there were no significant genotype differences across the three age groups” using a = .05. Do you agree?

Age Group E4+>E4+

Genotype E4+>E4-

Genotype E4->E4-

Genotype Sample Size 20–24 56 517 1,524 2,097 40–44 45 566 1,571 2,182 60–64 48 564 1,669 2,281