Chap 9 Grading Key -- DRAFT

Assigned 3/2 Due 3/9 Try In Class Honor System Self-Grade

9.10 cohort [observational, longitudinal, all case and non-cases studied]

9.11 cohort [observational, longitudinal, all case and non-cases studied]

9.12 randomized trial 

9.13 case-control, although an interpretation of cross-sectional is understandable. Depends on how you conceive of the exposure measurement. Current folic acid deficiency may be viewed as a surrogate for past folic acid deficiency, making a longitudinal interpretation reasonable. In addition, study selection seems to be based on disease status, adding further weight to the case-control classification. 

9.14 trial [cannot determine whether the intervention was randomized or not]

9.15 cohort 

9.16 cross-sectional

9.17 ecological [vital statistics by region = aggregate data]

9.18 ecological (The authors may have used some individual-level measurements and some aggregate-level measurements. Thus this might actually be a "multi-level" analysis.)

9.19 case-control (Pancreatic cancer is rare, on the order of 1 in a 100,000 per year. To get 189 case of pancreatic, you'd have to study a population for, say, 18.9 MILLION person-years. The study had only 1244 non-cases. Therefore, it is pretty clear that this is NOT a cohort study; since only a sample of population non-cases were studied.)