Doll & Hill hypothesized in 1950 that smoking was associated with stomach cancer. They decided to perform a case-control study to examine the relationship between this exposure and disease. They recruited 200 men aged 40-60 with a new diagnosis of stomach cancer. Participants were asked about their smoking behaviors during the 12 months before the interview. A total of 150 of the cases reported being smokers. Researchers were not sure the best way to select controls for this study. The following are 3 different scenarios of how researchers could have chosen controls for the study. Scenario A Researchers asked each case to select two close male friends aged 40-60 years without stomach cancer who would be interested in participating in the study. Out of the 400 best-friend controls 300 reported smoking. 1.A.1) Create a 2x2 table using the above information regarding cases and controls. Cases Controls (Stomach Cancer) (No Stomach Cancer) Smoked Never smoked 1.A.2) Calculate the odds ratio of smoking comparing cases and controls. (Show your work. Round final answer to 2 decimal places.) 1.A.3) Interpret the OR. + Scenario B Researchers decided to use patients aged 40-60 years with a different form of cancer to serve as controls. Researchers recruited 400 males with newly diagnosed lung cancer to serve as controls. Of the 400 controls, 336 reported smoking. 1.B.1) Create a 2x2 table using the above information regarding cases and controls. 1.B.2) Calculate the odds ratio of smoking comparing cases and controls. (Show your work. Round final answer to 2 decimal places.) 1.B.3) Interpret the OR. Scenario C Researchers used random digit dialing of close by neighborhoods to attempt to randomly recruit men aged 40-60 years as controls in the study. Of the 400 controls recruited, 153 reported smoking. 1.C.1) Create a 2x2 table using the above information regarding cases and controls. 1.C.2) Calculate the odds ratio of smoking comparing cases and controls. (Show your work. Round final answer to 2 decimal places) 1.C.3) Interpret the OR. Summary Questions: 1.D) Did the odds of exposure in the cases change in scenario 1, 2, and 3? 1.E) How can you explain the change in the odds ratios from scenarios 1, 2, and 3? 1.F) To optimize validity in this study, which control group would you choose and why? 1.G) There is a potential for differential recall (or recall rumination" (remembering) bias) in case-control studies, particularly when choosing healthy controls. Explain how differential recall might be present if selecting people from the general population as controls instead of sick people from a hospital?