Applied Statistics Workshop (Gov 3009)

Date: 

Wednesday, October 28, 2015, 12:00pm to 1:30pm

Location: 

K354, CGIS Knafel 1737 Cambridge St, Cambridge MA
The Applied Statistics Workshop (Gov 3009) meets all academic year, Wednesdays, 12pm-1:30pm, in CGIS K354. This workshop is a forum for advanced graduate students, faculty, and visiting scholars to present and discuss methodological or empirical work in progress in an interdisciplinary setting. The workshop features a tour of Harvard's statistical innovations and applications with weekly stops in different fields and disciplines and includes occasional presentations by invited speakers. There is a free lunch provided. Presentation by Judith Lok Title: Defining and estimating causal direct and indirect effects when setting the mediator to specific values is not feasible Abstract: Natural direct and indirect effects decompose the effect of a treatment into the part that is mediated by a covariate (the mediator) and the part that is not. Their definitions rely on the concept of outcomes under treatment with the mediator set'' to its value without treatment. Typically, the mechanism through which the mediator is set to this value is left unspecified, and in many applications it may be challenging to fix the mediator to particular values for each unit or individual. Moreover, how one sets the mediator may affect the distribution of the outcome. This presentation introduces organic'' direct and indirect effects, which can be defined and estimated without relying on setting the mediator to specific values. Organic direct and indirect effects can be applied for example to estimate how much of the effect of some treatments for HIV/AIDS on mother-to-child transmission of HIV-infection is mediated by the effect of the treatment on the HIV viral load in the blood of the mother. This presentation is based on two technical reports, which can be found on arxiv: http://arxiv.org/abs/1509.00351: Defining and estimating causal direct and indirect effects when setting the mediator to specific values is not feasible, Judith J Lok http://arxiv.org/abs/1510.02753: Organic direct and indirect effects with post-treatment common causes of mediator and outcome, Judith J Lok