Discussion:
Q1. Define Effect Size. Does increasing N increase Effect Size? Explain your answer with the Central Limit Theorem as your tool.
Q2. Assume that for the Quantitative GRE score, µ = 550 and σ = 50.
A sample of 25 students take the GRE after ingesting marijuana, the killer weed.
Their mean score is 530?less than a standard deviation below the population mean.
a) What is Cohen's d in this example? How would you (or Cohen) interpret this?
b) Which gives you more Power-- A 95% confidence interval or a 99% confidence interval? Show how you arrived at your answer.
c) Just for laughs, let's say that your sample of 25 students gets a mean score of 530.4. The parameters of the problem remain the same. Use whatever simplifying assumptions are necessary, and calculate power (with = .05) for this example.
d) Run the study again with 100 participants. The mean is still 530.4, and the standard deviation remain the same. With simplifying assumptions (and with α = .05), what is Power now?
e) Calculate Prep for the results of a Z test performed on the data in 2(c) above with N = 25.