new campus

While I am keeping my office at Porte Dauphine, undergoing major renovations (of the 1955 NATO building!), I am now spending most of my time in a more modern campus, called PariSanté, located at Porte de Versailles, with medical research teams and startups. This is where our master MASH will be located. The place is very luminous and despite the close proximity with the Paris beltway (le périf’), quiet (and much quieter than Paris Dauphine). It is also an ecological absurdity, with a huge sunroof that could not be shaded during the heat waves, plastic trees, self-induced lights, and compulsory lifts. On the memory lane, it is a trip back 35 years ago, as it sits across the road from the Balard military compound where I spent most of my military service in 1987 (working on my PhD in a research department).  And it is conveniently located half-way between home and Paris Dauphine, although not skipping the tough hill of Porte de Versailles on the way back..!

another Latin rectangle

simplified Bayesian analysis

A colleague from Dauphine sent me a paper by Carlo Graziani on a Bayesian analysis of vaccine efficiency, asking for my opinion. The Bayesian side is quite simple: given two Poisson observations, N~P(μ) and M~P(ν), there exists a reparameterisation of (μ,ν) into

e=1-μ/rν  and  λ=ν(1+(1-e)r)=μ+ν

vaccine efficiency and expectation of N+M, respectively, when r is the vaccine-to-placebo ratio of person-times at risk, ie the ratio of the numbers of participants in each group. Reparameterisation such that the likelihood factorises into a function of e and a function of λ. Using a product prior for this parameterisation leads to a posterior on e times a posterior on λ. This is a nice remark, which may have been made earlier (as for instance another approach to infer about e while treating λ as a nuisance parameter is to condition on N+M). The paper then proposes as an application of this remark an analysis of the results of three SARS-Cov-2 vaccines, meaning using the pairs (N,M) for each vaccine and deriving credible intervals, which sounds more like an exercise in basic Bayesian inference than a fundamental step in assessing the efficiency of the vaccines…

to bike or not to bike

A recent debate between the candidates to the Paris mayorship, including a former Health minister and physician, led to arguments as to whether or not biking in Paris is healthy. Obviously, it is beneficial for the community, but the question is rather about the personal benefits vs dangers of riding a bike daily to work. Extra physical activity on the one hand, exposition to air pollution and accidents on the other hand. With an accident rate that increased during the recent strikes, but at a lesser rate (153%) than the number of cyclists in the streets of Paris (260%). While I do not find the air particularly stinky or unpleasant on my daily 25km, except in the frequent jams between Porte d’Auteuil and Porte de la Muette, and while I haven’t noticed a direct impact on my breathing or general shape, I try to avoid rush hours, especially on the way back home with a good climb near Porte de Versailles (the more on days when it is jammed solid with delivery trucks for the nearby exhibition centre). As for accidents, trying to maintain constant vigilance and predicting potential fishtails is the rule, as is avoiding most bike paths as I find them much more accident-prone than main streets… (Green lights are also more dangerous than red lights, in my opinion!) Presumably, so far at least, benefits outweight the costs!

…place Dauphine…il est cinq heures, Paris s’éveille [jatp]