What are the approximate numbers of participants needed for each of the following planned studies to have 80% power, assuming equal numbers in the two groups and all using the .05 significance level? (Be sure to give the total number of participants needed, not just the number needed for each group.)

Expected

µ1 µ2 σ^2 Tails

(a) 10 15 25 1

(b) 10 30 25 1

(c) 10 30 40 1

(d) 10 15 25 2

What is the power of each of the following studies using a correlation coefficient and the .05 significance level?

Effect Size (r ) N Tails

(a) .10 30 1

(b) .30 40 2

(c) .50 50 2

(d) .30 100 2

(e) .10 20 1