AIPGMEE 2015

1. This is a multiplicative effect between exposure variables
   1. Biologic plausibility
   2. Confounder
   3. Effect modifier
   4. External validity
   5. Internal validity
   6. Intervening variable
   7. Measurement bias
   8. Necessary cause
   9. Recall bias
   10. Sufficient cause
   11. Synergism
        Answer K
2. When the combined effect of two or more variables on an outcome is greater than the sum of the separate effects of the variables, their interaction is called synergy or synergism. Cigarette smoking and asbestos exposure have a synergistic effect on the risk of lung cancer.† If the relative risk or risk ratio for lung cancer in smokers is X and if the relative risk for lung cancer in asbestos workers is Y, the relative risk in those with both exposures is closer to X × Y than to X + Y.