A researcher is interested in evaluating the risk factors for pancreatic cancer and determined whether the magnitude of cigarette smoking was modified by other risk factors in men and women. A hospital-based study was conducted involving 808 patients with pathologically diagnosed pancreatic cancer and 808 healthy frequency-matched controls. Information on risk factors was collected by personal interview. The following table summarizes the demographic features of the pancreatic cancer patients and controls: Picture1-2.png a. Is this an observational or experimental study? Explain your answer. (5 points) b. Write down the population and the sample for this study. (10 points) c. Considering the variable Duration of diabetes (1, >1, 2-5, 6-10, >10), identify the structure and type of it. (10 points) [Hint: structure - numerical or categorical; types -quantitative discrete, quantitative continuous or qualitative] d. Considering the variable Heavy alcohol drinking (60ml, >60ml), which graph/plot do you think is more an appropriate to display this variable? Explain your answer. (10 points)