study types measures of association and statistical test

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.

1.What type of study is this?

2.What is the independent variable in this scenario, and what type is it? What is the dependent variable in this scenario, and what type is it?

3.What is the most appropriate measure of association to evaluate the relationship of each risk factor with the occurrence of pancreatic cancer?

4.What is the most appropriate statistical test to test the significance of this measure of association?

5.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.First calculate the appropriate measure of association. Then, test it statistically using the on-line tool found at http://graphpad.com/quickcalcs/contingency2/. What are the results?

6.What do the results mean?

Scenario B: Another team of researchers set out to test a new medication developed to prevent the onset of diabetes in patients with a strong family history of diabetes.They assembled a group of 200 patients and randomized them into two groups, one to receive a placebo and the other to receive the medication.They followed them each year for five years and ascertained the occurrence of diabetes using a glucose tolerance test.

1.What type of study is this?

2.What is the independent variable in this scenario, and what type is it? What is the dependent variable in this scenario, and what type is it?

3.What is the most appropriate measure of association to evaluate the relationship of receipt of this medication with the development of diabetes?

4.What is the most appropriate statistical test to test the significance of this measure of association? (Assume that the outcome was just yes/no.Analysis dealing with “number of months/years to endpoint” is more complex than we intend to deal with for the purpose of this exercise.)

5.In this study, 9 of 100 patients receiving the medication developed diabetes, whereas 10 of 100 patients receiving the placebo developed diabetes.First calculate the appropriate measure of association.Then, test it statistically using the same on-line tool you used for problem #1.What are the results?

6.What do the results mean?