In a study of the effect of caffeine on muscle metabolism, nine male volunteers underwent arm exercise tests on two separate occasions. On one occasion, the volunteer took a placebo capsule an hour before the test; on the other occasion he received a capsule containing pure caffeine. (The time order of the two occasions was randomly determined.) During each exercise test, the subject's respiratory exchange ratio (RER) was measured. The RER is the ratio of carbon dioxide produced to oxygen consumed and is an indicator of whether energy is being obtained from carbohydrates or from fats. The results are presented in the accompanying table.32 Use a t test to assess the effect of caffeine. Use a non directional alternative and let α = 0.05.

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RER(96) Subject Plcebo Caffeine 105 119 92 97 96 101 96 89 95 95 95 98 93