Confounding V/s Effect modification
Confused between confounding and effect modification?? Here is the solution: 1- Confounding bias : Alcohol ( exposure ) Oral cancer ( outcome ) Smoking is a confounding bias here. Why ? Because smoking is related to BOTH the exposure and the outcome. People who smoke will more often than not, also drink, and people who have oral cancer, were probably smokers ( smoking is a known risk factor for oral cancer). 2- Effect modification : OCPs ( exposure ) Breast cancer (outcome ) Family history of breast cancer is an effect modification here. Can you guess why ? Asbestos ( exposure ) Lung cancer(outcome) Smoking is an effect modification Estrogens ( exposure ) DVT (outcome ) Smoking is an effect modification So do you notice the difference ?? The effect modification is ONLY related to the outcome, but NOT to the exposure. Think with me here : smoking does not effect neither asbestos exposure nor estrogen levels or intake,BUT definitely is a risk for lung cancer and DVT !! Family histo