Scientific

Epidemiologic methods are useless. They can only give you answers

Speaker:

Miguel Hernán

Date:

Fri, Mar 1, 2013

Location:

Michael Smith Laboratories, UBC

Conference:

Constance Van Eeden Speaker

Abstract:

The first duty of any epidemiologist is to ask a relevant
question. Learning and applying sophisticated epidemiologic methods is
of little help if the methods are used to answer irrelevant questions.
This talk will discuss the formulation of research questions in the
presence of time-varying treatments and treatments with multiple
versions, including pharmacological treatments and lifestyle
exposures. Several examples will show that discrepancies between
observational studies and randomized trials are often not due to
confounding, but to the different questions asked.

Brief Biography

Miguel Hernán is Professor of Department of Epidemiology and Department of Biostatistics at the Harvard School of Public Health (HSPH). His research is focused on the development and application of causal inference methods to guide policy and clinical interventions. He and his collaborators apply statistical methods to observational studies under suitable conditions to emulate hypothetical randomized experiments so that well-formulated causal questions can be investigated properly. His research applied to many areas, including investigation of the optimal use of antiretroviral therapy in patients infected with HIV, assessment of various interventions of kidney disease, cardiovascular disease, cancer and central nervous system diseases. He is Associate Director of HSPH Program on Causal Inference in Epidemiology and Allied Sciences, member of the Affiliated Faculty of the Harvard-MIT Division of Health Sciences and Technology, and an Editor of the journal EPIDEMIOLOGY. He is the author of upcoming highly anticipated textbook "Causal Inference" (Chapman & Hall/CRC, 2013), drafts of selected chapters are available on his website.

Class:

Subject:

Recent Results on Bootstrap Percolation

Speaker:

Béla Bollobás

Date:

Fri, Feb 15, 2013 to Sat, Feb 16, 2013

Location:

PIMS, University of British Columbia

Conference:

PIMS/UBC Distinguished Colloquium

Abstract:

Bootstrap percolation, one of the simplest cellular automata, can be viewed as an oversimplified model of the spread of an infection on a graph. In the past three decades, much work has been done on bootstrap percolation on finite grids of a given dimension in which the initially infected set A is obtained by selecting its vertices at random, with the same probability p, independently of all other choices. The focus has been on the critical probability, the value of p at which the probability of percolation (eventual full infection) is 1/2.

The first half of my talk will be a review of some of the fundamental results concerning critical probabilities proved by Aizenman, Lebowitz, Schonman, Cerf, Cirillo, Manzo, Holroyd and others, and by Balogh, Morris, Duminil-Copin and myself. The second half will about about the very recent results I have obtained with Holmgren, Smith, Uzzell and Balister on the time a random initial set takes to percolate.

Class:

Scientific

Subject:

Mathematics

Discrete Mathematics