Detecting Alzheimer’s disease at an early age. Refer to the Neuropsychology (Jan. 2007) st...

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. 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. (These data are saved in the E4E4ALL file.) The researchers concluded that “there were no significant genotype differences across the three age groups” using α = .05 . Do you agree?

Source: Jorm, A. F., et al. “APOE genotype and cognitive functioning in a large age-stratified population sample.” Neuropsychology , Vol. 21, No. 1, January 2007. Copyright © 2007 by the American Psychological Association. Reprinted with permission.

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Detecting Alzheimer’s disease at an early age. Geneticists at Australian National University are studying whether the cognitive effects of Alzheimer’s disease can be detected at an early age (Neuropsychology, Jan. 2007). One portion of the study focused on a particular strand of DNA extracted from each in a sample of 2,097 young adults between the ages of 20 and 24. The DNA strand was classified into one of three genotypes: E4+/E4+, E4+/E4- , and E4-/E4- . The number of young adults with each genotype is shown in the next table and the data are saved in the E4E4 file. Suppose that in adults who are not afflicted with Alzheimer’s disease, the distribution of genotypes for this strand of DNA is 2% with E4+/E4+ , 25% with E4+/E4- , and 73% with E4-/E4- . If differences in this distribution are detected, then this strand of DNA could lead researchers to an early test for the onset of Alzheimer’s. Conduct a test (at α = .05 ) to determine if the distribution of E4/E4 genotypes for the population of young adults differs from the norm.