Shoveling is not exactly a high-tech activity, but it will continue to be a required task even in our information age. The article "A Shovel with a Perforated Blade Reduces Energy Expenditure Required for Digging Wet Clay" (Human Factors, 2010: 492-502) reported on an experiment in which 13 workers were each provided with both a conventional shovel and a shovel whose blade was perforated with small holes. The authors of the cited article provided the following data on stable energy expenditure [(kcal/kg(subject)/lb(clay)]:

a. Calculate a confidence interval at the 95% confidence level for the true average difference between energy expenditure for the conventional shovel and the perforated shovel (the relevant normal probability plot shows a reasonably linear pattern). Based on this interval, does it appear that the shovels differ with respect to true average energy expenditure? Explain.
b. Carry out a test of hypotheses at significance level .05 to see if true average energy expenditure using the conventional shovel exceeds that using the perforated shovel.

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4 Worker Conventional: .0010014 0018 0022 Perforated: Worker: Conventional 0010 Perforated: Worker: Conventional Perforated: Worker Conventional: .0023 .0017 0020 Perforated: 0011 0010 0019 0013 0016 0028 001 0017 0024 10 0020 0015 0014 0020 0013 0013 12 0017 0015 0013