1. A study of the effect of caffeine on muscle metabolism used eighty male volunteers who each underwent arm exercise tests. Forty of the men were randomly selected to take a capsule containing pure caffeine one hour before the test. The other men received a placebo capsule. During each exercise the subject's respiratory exchange ratio (RER) was measured. (RER is the ratio of CO₂produced to O₂consumed and is an indicator of whether energy is being obtained from carbohydrates or fats).

Data found the sample of men who took the caffeine had an average RER of 94.22 with standard devation of 5.61, and the group who took the placebo had mean of 100.56 with standard deviation of 7.70.

The question of interest to the experimenter was whether, on average, caffeine changes RER. Test using a level of significance of .05