Scenario A: A team of researchers set out to study the risk factors for pancreatic cancer. From hospital records, they assembled a group of 50 patients who were either still living or who had a next of kin identified and willing to answer questions about medical history, lifestyle, and prior experiences of the patient. They assembled another group of 50 patients from the same hospital who were admitted for other causes and did not have cancer of any type. The investigators conducted a review of all available records of these patients, then interviewed them or their next of kin using a standardized format, either in person or by telephone. They focused on ten possible risk factors which could either be answered as yes/no or rated on an ordinal scale. In this study, 23 of the 50 pancreatic cancer patients were recorded as having at least a 20 pack-year history of cigarette smoking, while 8 of the 50 in the other group of patients had that history.
What is the Independent Variable in this scenario, and what TYPE is it? What is the dependent variable in this study and what TYPE is it? What might the null hypothesis be?