The article “Association Between Exposure to Emissions from the Oil and Gas Industry and Pathology of the Immune, Nervous, and Respiratory Systems, and Skeletal and Cardiac Muscle in Beef Calves” (C. Waldner and E. Clark, Annals of Environmental and Occupational Health, 2009:6–27) reports that in a sample of 355 calves less than 4 days old, 106 had lesions on their bronchial lymph nodes, while in a sample of 467 calves more than 4 days old, 147 had such lesions. Can you conclude that the proportion of calves with lesions differs between the two age groups?