- There is some evidence that REM sleep, associated with dreaming, may also play a role in learning and memory processing. For example, Smith and Lapp (1991) found increased REM activity for college students during exam periods. Suppose that REM activity for a sample of n=16 students during the final exam period produced an average score of M=143. Regular REM activity for the college population averages μ=110 with a standard deviation of σ=50. The population distribution is approximately normal.
a. Do the data from the sample provide evidence for a significant increase in REM activity during exams? Use a one-tailed test with α=.01
b. Compute Cohen’s d to estimate the size of the effect - If, for a particular sampling distribution of the mean, we know that the standard error is 4.6 and we also know that σ=32.2, what is the sample size (n)?
- Imagine that a test for spatial ability produces scores that are normally distributed with μ=60 and σ=20.
a. Between which two scores will you find the middle 80% of the population?
b. Considering the means of groups, all of which have 25 subjects, between what two scores will the middle 80% of these means be? - Although there is a popular belief that herbal remedies such as ginkgo biloba and ginseng may improve learning and memory in healthy adults, these effects are usually not supported by well-controlled research (Persson, Bringlov, Nillson & Nyberg, 2004). In a typical study, a researcher obtains a sample of n=36 participants and has each person take the supplements for 90 days. At the end of the 90 days, each person takes a standardized memory test. For the general population, scores from the test are normally distributed with mean μ=80 and a standard deviation of σ=18. The sample of research participants has an average of M=84.
a. Assuming a two-tailed test, state the null hypothesis in a sentence that includes the two variables being examined
b. Using symbols, state the null and alternative hypotheses for the two-tailed test
c. Sketch the appropriate distribution and locate the critical region for α=.05
d. What decision should be made about the null hypothesis, and what decision should be made about the effect of the herbal supplement? - A researcher is investigating the effectiveness of a new medication for lowering blood pressure for individuals with systolic pressure great than 140. For this population, systolic scores average μ=160 with a standard deviation of σ=20, and the scores form a normal distribution. The researcher plans to select a sample of n=25 individuals, and measure their systolic blood pressure after they take the medication for 60 days. Run the hypothesis with a one-tailed test with α=.05,
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