Since its removal from the banned substances list in 2004 by the World Anti-Doping Agency, caffeine has been used by athletes with the expectancy that it enhances their workout and performance. Many studies have been conducted to assess the effect of caffeine on athletes, but few look at the role it plays in sedentary females. Researchers at the University of Western Australia conducted a test in which they determined the rate of energy expenditure (kilojoules) on 10 healthy, sedentary females who were nonregular caffeine users.
Each female was randomly assigned either a placebo or caffeine pill (6 mg/kg) 60 minutes prior to exercise. The subject rode an exercise bicycle for 15 minutes at 65% of their maximum heart rate, and the energy expenditure was measured. The process was repeated on a separate day for the remaining treatment. The mean difference in energy expenditure (caffeine–placebo) was 18 kJ with a standard deviation of 19 kJ.
(a) State the null and alternative hypothesis to determine if caffeine increases energy expenditure.
(b) Assuming the differences are normally distributed, determine if caffeine appears to increase energy expenditure at the α = 0.05 level of significance.