Identify the explanatory and confounding variables in each of the following stud
ID: 3053876 • Letter: I
Question
Identify the explanatory and confounding variables in each of the following studies.
(a) To study whether removal of the breast or removal of only the tumor and nearby lymph nodes plus radiation is more effective for breast cancer, a team assigns some women to each treatment. However, because removal of a very large tumor is riskier, for the largest tumors, the entire breast was always removed. Survival times from the records of 25 hospitals are compared.
Explanatory: removal of breast or only tumor; confounding: hospitalExplanatory: tumor size; confounding: hospital Explanatory: removal of breast or only tumor; confounding: tumor sizeExplanatory: hospital; confounding: tumor sizeExplanatory: tumor size; confounding: removal of breast or only tumorExplanatory: hospital; confounding: removal of breast or only tumor
(b) According to a commentary in the Journal of the American Medical Association, "Thus, vitamin E enters the category of therapies that were promising in epidemiologic and observational studies but failed to deliver in adequately powered randomized controlled trials. As in other studies, the 'healthy user' bias must be considered, i.e., the heathy lifestyle behaviors that characterize individuals who care enough about their health to take various supplements are actually responsible for the better health, but this is minimized with the rigorous trial design."
Explanatory: healthy lifestyle behaviors; confounding: taking vitamin EExplanatory: taking other various supplements; confounding: healthy lifestyle behaviors Explanatory: taking vitamin E; confounding: healthy lifestyle behaviorsExplanatory: healthy lifestyle behaviors; confounding: taking other various supplementsExplanatory: taking vitamin E; confounding: taking other various supplementsExplanatory: taking other various supplements; confounding: taking vitamin E
(c) A nutritionist is interested in whether vitamin C is helpful for curing the common cold. A total of 60 people are exposed to a common cold virus, and then 20 are randomly assigned to a placebo group, while the other 40 take one of two doses of vitamin C. The nutritionist puts the 20 people not taking a placebo and with more symptoms on a higher dose of vitamin C, and those with fewer symptoms take a lower dose.
Explanatory: exposure to cold virus; confounding: symptomsExplanatory: symptoms; confounding: placebo, low dose, high dose Explanatory: placebo, low dose, high dose; confounding: symptomsExplanatory: exposure to cold virus; confounding: placebo, low dose, high doseExplanatory: placebo, low dose, high dose; confounding: exposure to cold virusExplanatory: symptoms; confounding: exposure to cold virus
Explanation / Answer
(a) Here explantory variable: removal of breast or only tumor as these two are the explanatory variables, where the variables are not independent
Confounding variable : It is the hospital as it influences both the dependent variable and independent variable causing a spurious association.
(b) Here explantory variables : Taking Vitamin E, as it is on that the study is based.
Confounding Variables : healthy lifestyle behaviors as these behaviors will either diminish or enhance the need to take vitamin E summpements.
(c) Here explantory variables : placebo, low dose, high dose as there are three different designs to check effectiveness of the vitamin C on cold.
Confounding Variables : Here confounding variables is symptoms, as each person has different immunity level so their may be symptioms or there may not by symptoms.