According to The Wellness Encyclopedia (University of California, 1991, p. 17): “Alcohol consumed to excess increases the risk of cancer of the mouth, pharynx, esophagus, and larynx. These risks increase dramatically when alcohol is used in conjunction with tobacco.” It is obviously not possible to conduct a designed experiment on humans to test this claim, so the causal con­clusion must be based on observational studies. Explain three potential additional pieces of in­formation that the authors may have used to lead them to make a causal conclusion. The following information applies to Exercises 14 to 16. Suppose a positive relationship had been found between each of the sets of variables given in Exercises 14 to 16. In Section 11.3, seven potential reasons for such relationships are given. Explain which of the seven reasons is most likely to account for the relationship in each case. If you think more than one reason might apply, mention them all but elaborate on only the one you think is most likely