Shoveling Heart Rates Because cardiac deaths appear to increase after heavy snowfalls, an experiment was designed to compare cardiac demands of snow shoveling to those of using an electric snow thrower. Ten subjects cleared tracts of snow using both methods, and their maximum heart rates (beats per minute, or BPM) were recorded during both activities. The results shown below were obtained (based on data from “Cardiac Demands of Heavy Snow Shoveling,”

by Franklin et al., Journal of the American Medical Association, Vol. 273, No. 11).

Manual Snow Shoveling: n = 10, x = 175 BPM, s = 15 BPM Electric Snow Thrower: n = 10, x = 124 BPM, x = 124, s = 18 BPM

a. Construct a 95% confidence interval estimate of the population standard deviation s for those who did manual snow shoveling.

b. Construct a 95% confidence interval estimate of the population standard deviation s for those who used the automated electric snow thrower.

c. Compare the results. Does the variation appear to be different for the two groups?