A study was done to compare the life expectancies of factory workers and office workers, looking at 200 of each occupation. There are other unexplored factors that might affect life expectancy, such as smoking habits, nutrition, and amount of exercise. The smoking habits of the two groups are similar, and their nutrition is appropriate, but the factory workers typically get more exercise. What conclusions can we come to about this study? Smoking habits and amount of exercise are negatively correlated. More exercise leads to greater life expectancy. Office workers will live longer than factory workers. Factory workers will need more nutrition than office workers. None, since we don't know the results