=+52. The degenerative disease osteoarthritis most frequently affects weight-bearing joints such as the knee. The article “Evidence of Mechanical Load Redistribution at the Knee Joint in the Elderly when Ascending Stairs and Ramps” (Annals of Biomed. Engr., 2008: 467–476) presented the following summary data on stance duration (ms) for samples of both older and younger adults.

Age Sample Size Sample Mean Sample SD Older 28 801 117 Younger 16 780 72 Assume that both stance duration distributions are normal.