Question

Problem 1 In a 5-year follow-up of bilateral stimulation of the subthalamic nucleus among 49 patients with advanced Parkinson's disease, investigators assessed changes in symptoms as measured by the Unified Parkinson's Disease Rating Scale (range = 0 to 108, with higher values denoting more symptoms). Assume this measure follows a normal distribution. The mean score at baseline was 55.7. The standard deviation of change from baseline to 5 years was 15.3. 1. How much power does this study have to detect a mean difference of 5 units in the symptom scale 2, what minimum sample size would be needed to detect a mean change of 5 units with 80% power 3. The above study had no control group. Assuming that the same standard deviation of change would if a two-sided test is used with a-0.05? if a two-sided test is used with a 0.05? occur among controls and the mean change among controls 0, how many participants would be necessary to detect a mean difference of 5 units of change between those receiving stimulation and a control group of equal size with 80% power if a two-sided test is used with α-005?

Answer 1