Does alcohol consumption cause increased cravings for cigarettes? Research at Purdue University suggests this is so (see CNN.com web site article “Researchers Find Link Between Cigarette Cravings and Alcohol,” dated June 13, 1997). In an experiment, 60 heavy smokers and moderate drinkers were divided into two groups. One group drank vodka tonics and the other group drank virgin tonics (tonic water alone), but all subjects were told they were drinking vodka tonics. The researchers then measured the level of nicotine cravings (by monitoring heart rate, skin conductance, etc.). Those who had consumed the vodka tonics had 35% more cravings than those who did not. Assuming that the assignment of subjects to the treatment (vodka) and control groups was made at random, do you think there are any confounding factors that would make conclusions based on this experiment questionable?