Final answer:
Tommy is committing the fallacy of composition by assuming that playing football will make him big and strong based on the observation that people who play football are larger than average.
Step-by-step explanation:
Tommy is committing the fallacy of composition. The fallacy of composition occurs when a person assumes that what is true for the parts must also be true for the whole. In this case, Tommy observes that individuals who play football are larger than average, and he assumes that playing football will make him big and strong. However, this assumption does not necessarily hold true for everyone who plays football. While it is true that some football players may be larger and stronger due to their involvement in the sport, there are many factors that contribute to an individual's size and strength. Therefore, Tommy is incorrect in his assumption that playing football will make him big and strong.