Because cardiac deaths appear to increase after heavy snowfalls, astudy was desi
ID: 2950956 • Letter: B
Question
Because cardiac deaths appear to increase after heavy snowfalls, astudywas designed to compare cardiac demands of snow shoveling to thoseof using an
electric snow thrower. Ten subjects cleared tracts of snow usingboth methods,
and their maximum heart rates were recorded during both activities.The following results were obtained (based on data from "CardiacDemands of Heavy Snow Shoveling," by Franklin et a., Journal ofthe American Medical Association, Vol. 273, No. 11):
Manual snow shoveling maximum heart rates: n = 10, x =175, s = 15
Electric snow thrower maximum heart rates: n= 10, x = 175,s = 15
a. Find the 95% confidence interval estimate of the population meanfor those people who shovel snow manually.
b. Find the 95% confidence interval estimate of the population meanfor those people who use the electric snow thrower.
c. If you are a physician with concerns about cardiac deathsfostered by manual snow shoveling, what single value in theconfidence interval from part (a) would be of greatest concern?
d. Compare the confidence intervals from parts (a) and (b) andinterpret your findings.
Explanation / Answer
95% confidence interval --> p = .975 and .025 --> z =±1.96 A) SE = stdev(X) / sqrt(n) = 15 / sqrt(10) = 4.74 CI = ± z * SE = 175 ± 1.96 * 4.74 = [165.71,184.29] B) SE = 15 / sqrt(10) = 4.74 CI = 175 ± 1.96 * 4.74 = [165.71, 184.29] D) Since the confidence intervals overlap (and in this case areidentical), there is no statistically significant difference in maxheart rate between manually shoveling an using an electric snowthrower.