1. In a random sample of 280 cars driven at sea level, 38 of them produced more than 10 g of particulate pollution per gallon of fuel consumed. In a random sample of 77 cars driven at a higher elevation, 18 of them produced more than 10 g of particulate pollution per gallon of fuel consumed. Can you conclude that the proportion of cars whose emissions exceed 10 g per gallon is greater at the higher elevation?
2. The article "Modeling the Inactivation of Particle- Associated Coliform Bacteria" (R. Emerick, F. Loge, et al., Water Environment Research, 2000:432-438) presents counts of the numbers of particles of various sizes in wastewater samples that contained coliform bacteria. Out of 161 particles 75-80 µm in diameter, 19 contained coliform bacteria, and out of 95 particles 90-95 µm in diameter, 22 contained coliform bacte- ria. Can you conclude that the larger particles are more likely to contain coliform bacteria?