How does each of the following affect the power of a planned study? a) A larger predicted difference between the means of the populations. b) A larger population standard deviation. c) A larger sample size. d) Using a more extreme significance level (e.g., .01 instead of .05). e) Using a two-tailed test instead of a one-tailed test. Explain why these would be the answers: a) Increases power; b) decreases power; c) increases power; d) decreases power; e) decreases power