20. A researcher plans to conduct an experiment evalu-
ating the effect of a treatment. A sample of n = 9
participants is selected and each person receives the
treatment before being tested on a standardized dex-
terity task. The treatment is expected to lower scores
on the test by an average of 30 points. For the regular
population, scores on the dexterity task form a normal
distribution with u = 240 and σ = 30.
a. If the researcher uses a two-tailed test with weib
a = .05, what is the power of the hypothesis test?
b. Again assuming a two-tailed test with a = = .05,
what is the power of the hypothesis test if the
sample size is increased to n = 25?