Question: A study to determine whether a new drug to treat a specific brain tumor was
administered to 100 patients. The old treatment had a standard deviation of 18 months, and the new treatment was thought to have similar variability from patient to patient. The investigators calculated that their study would have 80% power if the new drug would lengthen the average survival by 5 months. What would happen to the power of the test, would it go up, down, or stay the same, if:
a) The study had 200 subjects (instead of the 100 in the original design)?
b) The new drug improved survival 3 months (instead of the 5 months originally thought)
c) The σ of survival time was actually 24 months (instead of the original 18 months)?