Katherine Tucker and associates wanted to determine whether consumption of cola is associated with lower bone mineral density. They looked at 1125 men and 1413 women in the Framingham Osteoporosis Study, which is a cohort that began in 1971. The first examination in this study began between 1971 and 1975, with participants returning for an examination every 4 years. Based on results of questionnaires, the researchers were able to determine cola consumption on a weekly basis. Analysis of the results indicated that women who consumed at least one cola per day (on average) had a bone mineral density that was significantly lower at the femoral neck than those who consumed less than one cola per day. The researchers did not find this relation in men.
(a) Why is this a cohort study?
(b) What is the response variable in this study? What is the explanatory variable?
(c) Is the response variable qualitative or quantitative?
(d) The following appears in the article: “Variables that could potentially confound the relation between carbonated beverage consumption and bone mineral density were obtained from information collected (in the questionnaire).” What does this mean?
(e) Can you think of any lurking variables that should be accounted for?
(f ) What are the conclusions of the study? Does increased cola consumption cause a lower bone mineral density?