Question

Hours of sleep: The table below provides information about hours of sleep.

1. Calculate statistical power for a one-tailed test (a = 0.05, or 5%) aimed at determining if those in the sample sleep fewer hours, on average, than those in the population.
2. Recalculate statistical power with alpha of 0.01, or 1%. Explain why changing alpha affects power. Explain why we should not use a larger alpha to increase power.
3. Without performing any computations, describe how statistical power is affected by performing a two-tailed test for this example. Why are two-tailed tests recommended over one-tailed tests?
4. The easiest way to affect the outcome of a hypothesis test is to increase sample size. Similarly, true results may sometimes be missed because a sufficient sample was not used in the research. Perform the hypothesis test on these data with a sample of 37. Then perform the same hypothesis test but assume that the mean was based on only 4 infants.
5. The easiest way to increase statistical power is to increase sample size. Similarly, statistical power decreases with a smaller sample size. For these data, compute the statistical power of the one-tailed statistical test with alpha of 0.05 when N is 4. How does that value compare to when N was 37?

Mean of population 1 (from which the sample comes)	14.9 hours of sleep
Sample size	37 infants
Mean of population 2	16 hours of sleep
Standard deviation of the population	1.7 hours of sleep
Standard error

Answer 1