A dealer advertises that a certain brand of tire averages 50,000 miles of use before needing to be replaced. Testing this claim, an investigator finds that a sample of 19 randomly selected tires from this dealer had an average lifespan of 48,700 miles with a standard deviation of 4,500 miles. Assume tire life spans are approximately normally distributed. At the α = 0.05 level, find if the investigator can prove the dealer is exaggerating the average lifespan of their tires by performing the hypothesis test.