Researchers have noted a decline in cognitive functioning as people age (Bartus, 1990). However, the results from other researchessuggest that the antioxidantsin foods such as blueberries can reduce and even reverse these age-related declines, at least in laboratory rats (Joseph et al., 1999). Based on these results, one might theorize that the same antioxidants might alsobenefit elderly humans. Supposea researcher is interested in testing this theory. The researcherobtains a sample of n=16 adults who are older than 65, and giveseach participant a daily dose of a blueberry supplement that is very high in antioxidants. After taking the supplement for 6 months, the participants are given a standardized cognitive skills testand produce a mean score of M=50.2. For the general population of elderly adults, scores on the test average=45 and form a normal distribution with=9. Can the researcher conclude that the supplement has a significant effect on cognitive skill? use a two-tailed test with=0.05.

1)state hypothesis with symbols and statement (2points)

2)determine the z-critical boundary score with the alpha level (1point)

3) compute the z-statistic (please show all your calculation) (2 points)

4)make a decision (3 points)

5) do you need to compute Cohen's d ? why? if so, what is the Cohen's d (2 points)