9.65 Power for knee osteoarthritis treatment An ankle-foot orthosis (AFO) is a specially designed brace to support and improve the function of the foot and ankle. A 2016 study on the treatment of knee osteoarthritis investigated the biomechanical effects of the Agilium Freestep AFO on the lever arm of the ground reaction force (GRF) in a gait analysis lab. Results show that the lever arm of the GRF was significantly reduced by 14% with the Agilium Freestep AFO (www.oandp.org). Statistical analyses were conducted using the Student’s t-test with a power of 80%.

a. What should be the null and the alternative hypotheses in this study?

b. How should the power of 80% be interpreted?

c. In context, what is a Type II error for this test?