A researcher plans to conduct an experiment testing the effect of caffeine on reaction time during a driving simulation task. A sample of n = 9 participants is selected and each person receives a standard dose of caffeine before being tested on the simulator. The caffeine is expected to lower reaction time by an average of 30 msec. Scores on the simulator task for the regular population (without caffeine) form a normal distribution with µ = 240 msec. and σ = 30.

a. If the researcher uses a two-tailed test with α = .05, what is the power of the hypothesis test?

b. Again assuming a two-tailed test with α = .05, what is the power of the hypothesis test if the sample size is increased to n = 25?