[gov3009-l] Applied Statistics - 4/15 - Tyler VanderWeele

Anton Strezhnev astrezhnev at fas.harvard.edu
Mon Apr 13 10:48:47 EDT 2015


Hi everyone!

This week at the Applied Statistics Workshop we will be welcoming *Tyler
VanderWeele*, a Professor of Epidemiology at the Harvard School of Public
Health.  He will be presenting work entitled *A Unification of Mediation
and Interaction: A 4-Way Decomposition*.  Please find the abstract below
and on the website
<http://projects.iq.harvard.edu/applied.stats.workshop-gov3009/presentations/tyler-vanderweele-harvard>
.

As usual, we will meet in CGIS Knafel Room 354 and lunch will be provided.
See you all there!

-- Anton

Title: A Unification of Mediation and Interaction: A 4-Way Decomposition

Abstract:  The overall effect of an exposure on an outcome, in the presence
of a mediator with which the exposure may interact, can be decomposed into
4 components: (1) the effect of the exposure in the absence of the
mediator, (2) the interactive effect when the mediator is left to what it
would be in the absence of exposure, (3) a mediated interaction, and (4) a
pure mediated effect. These 4 components, respectively, correspond to the
portion of the effect that is due to neither mediation nor interaction, to
just interaction (but not mediation), to both mediation and interaction,
and to just mediation (but not interaction). This 4-way decomposition
unites methods that attribute effects to interactions and methods that
assess mediation. Certain combinations of these 4 components correspond to
measures for mediation, whereas other combinations correspond to measures
of interaction previously proposed in the literature. Prior decompositions
in the literature are in essence special cases of this 4-way decomposition.
The 4-way decomposition can be carried out using standard statistical
models, and software is provided to estimate each of the 4 components. The
4-way decomposition provides maximum insight into how much of an effect is
mediated, how much is due to interaction, how much is due to both mediation
and interaction together, and how much is due to neither.
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