results, one might theorize that the same antioxi- dants might also benefit elderly humans. Suppose a researcher is interested in testing this theory. The researcher obtains a sample of n = 16 adults who are older than 65, and gives each participant a daily dose of a blueberry supplement that is very high in antioxi- dants. After taking the supplement for 6 months, the participants are given a standardized cognitive skills test and produce a mean score of M = 50.2. For the general population of elderly adults, scores on the test average 45 and forma normal distribution with o =9 a. Can the researcher conclude that the supplement has a significant effect on cognitive skill? Use a two-tailed test with a = .05 b. Compute Cohen's d for this study. c. Write a sentence demonstrating how the outcome of the hypothesis test and the measure of effect size would appear in a research report. (Liguori of caf- In a ne ce cup for with of e has - it h- 19. A researcher is evaluating the influence of a treatment using a sample selected from a normally distributed population with a mean of u= 40 and a standard deviation of o = 12. The researcher expects a 6-point f 266 CHAPTER 8 | Introduction to Hypothesis Testing and pl treatment effect and plans to use a two-tailed hypoth- esis test with a= .05 n 2 ago, t ized d a. Compute the power of the test if the researcher uses a sample of n =9 individuals. (See Example 8.6.) b. Compute the power of the test if the researcher uses a sample of n 16 individuals. stand а 7-р 10 y for 20. A researcher plans to conduct an experiment evalu- ating the effect of a treatment. A sample of n=9 participants is selected and each person receives the treatment before being tested on a standardized dex- terity task. The treatment is expected to lower scores on the test by an average of 30 points. For the regular poulation, scores on the dexterity task form a normal distribution with u = 240 and o 30. a. If the researcher uses a two-tailed test with а. b. 22. В a = .05, what is the power of the hypothesis test? b. Again assuming a two-tailed test with o = .05, what is the power of the hypothesis test if the sample size is increased to n = 25? 21. Research has shown that IQ scores have been increas- ing for years (Flynn, 1984, 1999). The phenomenon is called the Flynn effect and the data indicate that the increase appears to average about 7 points per decade. To examine this effect, a researcher obtains an IQ test 23. structions for scoring