Archive for COSMOSTATS 09

A Mountain of Truth

Posted in Bad Statistics, The Universe and Stuff with tags , , , , on August 1, 2009 by telescoper

I spent the last week at a conference in a beautiful setting amidst the hills overlooking the small town of Ascona by Lake Maggiore in the canton of Ticino, the Italian-speaking part of Switzerland. To be more precise we were located in a conference centre called the Centro Stefano Franscini on  Monte Verità. The meeting was COSMOSTATS which aimed

… to bring together world-class leading figures in cosmology and particle physics, as well as renowned statisticians, in order to exchange knowledge and experience in dealing with large and complex data sets, and to meet the challenge of upcoming large cosmological surveys.

Although I didn’t know much about the location beforehand it turns out to have an extremely interesting history, going back about a hundred years. The first people to settle there, around the end of the 19th Century,  were anarchists who had sought refuge there during times of political upheaval. The Locarno region had long been a popular place for people with “alternative” lifestyles. Monte Verità (“The Mountain of Truth”) was eventually bought by Henri Oedenkoven, the son of a rich industrialist, and he  set up a sort of commune there at  which the residents practised vegetarianism, naturism, free love  and other forms of behaviour that were intended as a reaction against the scientific and technological progress of the time.  From about 1904 onward the centre became a sanatorium where the discipline of psychoanalysis flourished and it later attracted many artists. In 1927,   Baron Eduard Von dey Heydt took the place over. He was a great connoisseur of Oriental philosophy and art collector and he established  a large collection at Monte Verità, much of which is still there because when the Baron died in 1956 he left Monte Verità to the local Canton.

Given the bizarre collection of anarchists, naturists, theosophists (and even vegetarians) that used to live in Monte Verità, it is by no means out of keeping with the tradition that it should eventually play host to a conference of cosmologists and statisticians.

The  conference itself was interesting, and I was lucky enough to get to chair a session with three particularly interesting talks in it. In general, though, these dialogues between statisticians and physicists don’t seem to be as productive as one might have hoped. I’ve been to a few now, and although there’s a lot of enjoyable polemic they don’t work too well at changing anyone’s opinion or providing new insights.

We may now have mountains of new data in cosmology in particle physics but that hasn’t always translated into a corresponding mountain of truth. Intervening between our theories and observations lies the vexed question of how best to analyse the data and what the results actually mean. As always, lurking in the background, was the long-running conflict between adherents of the Bayesian and frequentist interpretations of probability. It appears that cosmologists -at least those represented at this meeting – tend to be Bayesian while particle physicists are almost exclusively frequentist. I’ll refrain from commenting on what this might mean. However, I was perplexed by various comments made during the conference about the issue of coverage. which is discussed rather nicely in some detail here. To me the question of of whether a Bayesian method has good frequentist coverage properties  is completely irrelevant. Bayesian methods ask different questions (actually, ones to which scientists want to know the answer) so it is not surprising that they give different answers. Measuring a Bayesian method according to  a frequentist criterion is completely pointless whichever camp you belong to.

The irrelevance of coverage was one thing that the previous residents knew better than some of the conference guests:

mvtanz3

I’d like to thank  Uros Seljak, Roberto Trotta and Martin Kunz for organizing the meeting in such a  picturesque and intriguing place.

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