Introduction to Hypothesis Testing 266 CHAPTER 8 and plans to administers the test to a sample of 25 of today's high school students. Ten ago, the scores on this IQ test produced a standard- ized distribution with a mean of p standard deviation o = treatment effect and plans to use a two-tailed hypoth- esis test with a years n = = .05. 100 and a a. Compute the power of the test if the researcher uses 9 individuals. (See Example 8.6.) of the test if the researcher 15. If there actually has been a sample of n a 7-point increase in the average IQ during the 10 years, then find the power of the hypothesis test b. Compute past the power 16 individuals. uses a sample of n 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 population, scores on the dexterity task form a normal distribution with u for each of the following. a. The researcher uses a two-tailed hypothesis test .05 to determine if the data indicate a 10 with a = significant change in IQ over the past b. The researcher uses a one-tailed hypothesis test with a years. .05 to determine if the data indicate a past 10 years. significant increase in IQ over the 240 and o = 30. 22. Briefly explain how increasing sample size influences each of the following. Assume that all other factors a. If the researcher uses a two-tailed test with a= .05, what is the power of the hypothesis test? are held constant. b. Again assuming a two-tailed test witha = .05, a. The size of the z-score in a hypothesis test. b. The size of Cohen's d. what is the of the hypothesis test if the power sample size is increased to n 25? of a hypothesis test. The с. power 21. Research has shown that IQ scores have been increas- ing for is called the Flynn effect and the data indicate that the increase years (Flynn, 1984, 1999). The phenomenon 23. Explain how the power of a hypothesis test is influ- enced by each of the following. Assume that all other factors are held constant. about 7 points per to decade. appears average To examine this effect, a researcher obtains an IQ test a. Increasing the alpha level from .01 to .05. b. Changing from a one-tailed test to a two-tailed test. with instructions for scoring from 10 years ago