2) The degenerative disease osteoarthritis most frequently affects weight-bearing joints such as 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. Carry out a test of hypotheses at significance level .05 to decide whether true average stance duration is larger among elderly individuals than among younger individuals. (Population variances are not assumed equal.)