Archive for Jim Berger

Savage-Dickey [talk]

Posted in R, Statistics, Travel with tags , , , , , , on March 19, 2010 by xi'an

Here are the slides for the Savage-Dickey paradox paper that I gave in San Antonio this morning:

(Any suspected coincidence of the first part with earlier talks is for real!) I have tried to spell out as clearly as possible in the second part the issues of version choices that are at the core of the “paradox”.

Short Monte Carlo course in San Antonio

Posted in R, Statistics, Travel with tags , , on January 22, 2010 by xi'an

Just a reminder that I will teach a very short course on March 17 in San Antonio, Texas, based on our “Introducing Monte Carlo Methods with R” book, in the first day of the meeting  Frontiers of Statistical Decision Making and Bayesian Analysis, in honour of Jim Berger, There still are a few places left on the four courses provided that day, register now!

Bayes factor approximations

Posted in Statistics with tags , , , , , , on October 14, 2009 by xi'an

Following Andrew Gelman by a few days, we have now finished with Jean-Michel Marin a survey on importance sampling methods for Bayes factor approximations which is our contribution to a book of essays, Frontiers of Statistical Decision Making and Bayesian Analysis, in honour of Jim Berger, published in conjunction with a conference with the same name, next March, in San Antonio, Texas. When I was young, so much younger than today, I could not see the point of those celebration conferences. I am not sure I have gotten any wiser with age, but I do see a point in celebrating Jim Berger! First, Jim has contributed and is contributing immensely to statistical science from many respects, first and foremost in grounding Bayesian analysis within decision theory. His book Statistical Decision Theory and Bayesian Analysis has influenced many readers and this is certainly the (statistics) book that has had the most influence upon me, as can be seen in The Bayesian Choice. His works on Bayesian testing are fundamental for the understanding of the specific nature of this approach and his earlier advances in shrinkage estimations have determined the field. On a more personal basis, Jim Berger has always been immensely helpful and supportive, starting with his invitation to Purdue in 1987 when I was fresh out of my PhD… So, yes indeed !, I am now quite glad to see this conference in his honour taking place so that we can all thank him!

The survey with Jean-Michel, now posted on arXiv, is linked with some older work of Jim in that he was studying importance sampling methods with Man-Suk Oh at the time I was visiting Purdue, in the pre-MCMC days. The toolkit for approximating Bayes factors has considerably grown in the past twenty years but importance sampling, albeit in a refined format, remains a central methodology. In the probit example we provide in the survey, this is actually the best method, thanks to a very good approximation of the posterior by the normal asymptotic approximation to the likelihood, as already shown in the entry on Savage-Dickey posted a few days ago. In this same example, the harmonic mean estimator of the marginal is doing surprisingly well, again because of the fit of the approximation.

Yes III slides

Posted in Statistics, University life with tags , , on October 7, 2009 by xi'an

After modifying my slides for the Yes III workshop by (a) including a Monte Carlo comparison between importance sampling methods (done in a survey paper with Jean-Michel Marin in preparation for the conference in honour of Jim Berger) and (b) covering the Savage-Dickey latest develoments (another paper soon to be posted), I put those slides on slideshare:

(Warning: the changes only are in the importance sampling section)