EHS 260 Lecture Notes - Lecture 17: Odds Ratio, Absolute Difference, Relative Risk
7 May 2016
School
Department
Course
Professor
Document Summary
When dealing with exposures that are associated with a decreased risk of disease (often the case for pa) researchers sometimes take the unexposed group (the inactive group) as the reference category. Odds ratio (similar to relative risk, used in many case-control studies); Comparison of disease occurrence between exposed and unexposed groups. Example: smokers vs. non-smokers sedentary people vs. physically active people. The absolute difference in rates of occurrence between groups of individuals who have and who have not been exposed to the factor of interest. The ratio of the risk of occurrence among exposed people to that among unexposed. It measures the strength of an association. Let"s assume that the incidence of stroke is 17. 7 per 100,000person-years among non- smokers and 49. 6 per 100,000 person years among smokers. The relative risk of stroke in smokers compared with non-smokers is therefore 2. 8 (49. 6/17. 7) In other words, smokers are 2. 8 times more likely to have a stroke than non-smokers.
