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Interaction and effect modification are formally defined within the counterfactual framework. Interaction is defined in terms of the effects of 2 interventions whereas effect modification is defined in terms of the effect of one intervention varying across strata of a second variable. Effect modification can be present with no interaction ...
Effect modification also involves a third variable (not the exposure and not the outcome)—but in this case, we absolutely do not want to control for it. Rather, presence of effect modification is itself an interesting finding, and we highlight it. When effect modification (also called interaction) is present, there will be different results ...
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The difference between these terms is rather subtle and has been described in Effect modification, interaction and mediation: an overview of theoretical insights for clinical investigators (Clin Epidemiol 2017;9:331-8) and in Tutorial: A nontechnical explanation of the counterfactual definition of effect modification and interaction (J. Clin ...
Confounding. A situation in which the effect or association between an exposure and outcome is distorted by the presence of another variable. Positive confounding (when the observed association is biased away from the null) and negative confounding (when the observed association is biased toward the null) both occur. Effect modification.
Keywords: effect modification, interaction, synergism, confounding, moderation. DOI 10.1515/em-2013-0005. It is not uncommon for the effect of one exposure on an outcome to depend in some way on the presence or absence of another exposure. When this is the case, we say that there is interaction between the two exposures.
Nov 11, 2008 · tion 1 for effect modification was that of a conditioning variable. Thus, Q is a conditioning variable in the definition of effect modification, and an intervention variable in the definition of interaction. This distinction between effect modification and interaction also underlies the examples given in the following sections.
Sep 16, 2015 · For the second phenomenon, effect modification means that the mechanism of effect differs with background variables, which is known in the biomedical literature as dependent action or (again) interaction. The two phenomena are often confused, as reflected by the use of the same terms ( effect modification and interaction) for both.
