Introduction-to-Statistics-and-Quantitative-Research-Methods

What if there is an effect?• Odds Ratio (OR) is a way of comparing whether the probability ofa certain event is the same for two groups.• Used for cross-sectional studies, case control trials, andretrospective trials.• In case control studies you can't estimate the rate of diseaseamong study subjects because subjects selected according todisease/no disease. So, you can't take the rate of disease in bothpopulations (in order to calculate RR).• OR is the comparison between the odds of exposure amongcases to the odds of exposure among controls.• Odds are same as betting odds. Example: if you have a 1 in 3chance of winning a draw, your odds are 1:2.• To calculate OR, take the odds of exposure (cases)/odds ofexposure (controls).• E.g. Smokers are 2.3 times more likely to develop lung cancerthan non-smokers.