22. To test whether memory changes with age, a researcher conducts an experiment in which there are four groups of six subjects each. The groups differ according to the age of subjects. In group 1, the subjects are each 30 years old; group 2, 40 years old; group 3, 50 years old; and group 4, 60 years old. Assume that the subjects are all in good health and that the groups are matched on other important variables such as years of education, IQ, gender, motivation, and so on. Each subject is shown a series of nonsense syllables (a meaningless combination of three letters such as DAF or FUM) at a rate of one syllable every 4 seconds. The series is shown twice, after which the subjects are asked to write down as many of the syllables as they can remember. The number of syllables remembered by each subject is shown here:
30 Years Old 40 Years Old 50 Years Old 60 Years Old 14 12 17 13 13 15 14 10 15 16 14 7 17 11 9 8 12 12 13 6 10 18 15 9

a. Use the analysis of variance with   0.05 to determine whether age has an effect on memory.

b. If there is a signifi cant effect in part

a, determine the size of effect, using ˆ 2.

c. Determine the size of effect, using 2.

d. Explain the difference in answers between part b and part c.

e. Using planned comparisons with   0.052 tail, compare the means of the 60-year-old and the 30-year-old groups. What do you conclude?

f. Use the Scheffé test with   0.05 to compare all possible pairs of means. What do you conclude?
cognitive