OR (Odds Ratio)

Instead of investigating the chance of going 13 months without a root canal your practice is only interested in the chance of having a root canal given various exposures, so you decide to do a case-control study. Suppose that for every root canal case from the previous 18 months, 3 controls were selected and both cases (43} and controls (129) were asked the about various exposures. a. Fill in the ORs for all the exposures in the table below (counts in the table are for those patients who had the exposure). For each OR use the odds of having the particular exposure in cases compared to controls. (8pts) IN PREP mmm_ - --_ Floss regularly _ _-_ - revious 6 months _E_ _ b. Which of these exposures appear to be protective and which appear harmful? (Zpts) c. What doesn't appear to have any association? (1pt) d. If the cases are those from the first study how does that impact your interpretation of the above 0R5? (Zpts) e. If the controls are a random selection of anyone who did not have a filling in a molar vs. those who did, how might that impact the 0R5? (Zptsl