Archive for Paris

heart of Paris

Posted in pictures, Travel with tags , , , , , , , , , , on April 17, 2019 by xi'an

Notre Drame

Posted in Books, pictures, Travel with tags , , , , , , , , on April 16, 2019 by xi'an

Gone…! [Ash Monday]

Posted in Books, Kids, pictures, Travel with tags , , , , , , , , , on April 15, 2019 by xi'an

Even stronger and farther-reaching a symbol of Paris than the Eiffel Tower, the Notre-Dame-de-Paris cathedral is now burning down. Only Hugo can make for the memory of this monumental loss:

“Sur la face de cette vieille reine de nos cathédrales, à côté d’une ride on trouve toujours une cicatrice. Tempua edax, homo edacior; ce que je traduirais volontiers ainsi: le temps est aveugle, l’homme est stupide.” Victor Hugo, Notre-Dame-de-Paris, 1831

“Notre-Dame est aujourd’hui déserte, inanimée, morte. On sent qu’il y a quelque chose de disparu. Ce corps immense est vide; c’est un squelette; l’esprit l’a quitté, on en voit la place, et voilà tout.” Victor Hugo, Notre-Dame-de-Paris, 1831

“Tous les yeux s’étaient levés vers le haut de l’église. Ce qu’ils voyaient était extraordinaire. Sur le sommet de la galerie la plus élevée, plus haut que la rosace centrale, il y avait une grande flamme qui montait entre les deux clochers avec des tourbillons d’étincelles, une grande flamme désordonnée et furieuse dont le vent emportait par moments un lambeau dans la fumée. ” Victor Hugo, Notre-Dame-de-Paris, 1831

The spire is gone. The roof is gone. What’s terrible is that it survived the French revolution, which wanted to tear it down, the 1870 siege of Paris by Prussian troops, the Commune de Paris, the 1914-1918 canon bombs from German guns, the 1944 air bombings by Allied planes. (Once again an accidental fire started by maintenance works. As in the Brazilian Museum of Natural History, Windsor Castle, Glasgow, Rennes, &tc.)

absint[he] post-doc on approximate Bayesian inference in Paris, Montpellier and Oxford

Posted in Statistics with tags , , , , , , , , , , , , , on March 18, 2019 by xi'an

As a consequence of its funding by the Agence Nationale de la Recherche (ANR) in 2018, the ABSint research conglomerate is now actively recruiting a post-doctoral collaborator for up to 24 months. The accronym ABSint stands for Approximate Bayesian solutions for inference on large datasets and complex models. The ABSint conglomerate involves researchers located in Paris, Saclay, Montpelliers, as well as Lyon, Marseille, Nice. This call seeks candidates with an excellent research record and who are interested to collaborate with local researchers on approximate Bayesian techniques like ABC, variational Bayes, PAC-Bayes, Bayesian non-parametrics, scalable MCMC, and related topics. A potential direction of research would be the derivation of new Bayesian tools for model checking in such complex environments. The post-doctoral collaborator will be primarily located in Université Paris-Dauphine, with supported periods in Oxford and visits to Montpellier. No teaching duty is attached to this research position.

Applications can be submitted in either English or French. Sufficient working fluency in English is required. While mastering some French does help with daily life in France (!), it is not a prerequisite. The candidate must hold a PhD degree by the date of application (not the date of employment). Position opens on July 01, with possible accommodation for a later start in September or October.

Deadline for application is April 30 or until position filled. Estimated gross salary is around 2500 EUR, depending on experience (years) since PhD. Candidates should contact Christian Robert (gmail address: bayesianstatistics) with a detailed vita (CV) and a motivation letter including a research plan. Letters of recommendation may also be emailed to the same address.

how a hiring quota failed [or not]

Posted in Books, Statistics, University life with tags , , , , , , , , , , , , , on February 26, 2019 by xi'an

This week, Nature has a “career news” section dedicated to how hiring quotas [may have] failed for French university hiring. And based solely on a technical report by a Science Po’ Paris researcher. The hiring quota means that every hiring committee for a French public university hiring committee must be made of at least 40% members of each gender.  (Plus at least 50% of external members.) Which has been reduced to 30% in some severely imbalanced fields like mathematics. The main conclusion of the report is that the reform has had a negative impact on the hiring imbalance between men and women in French universities, with “the higher the share of women in a committee, the lower women are ranked” (p.2). As head of the hiring board in maths at Dauphine, which officiates as a secretarial committee for assembling all hiring committee, I was interested in the reasons for this perceived impact, as I had not observed it at my [first order remote] level. As a warning the discussion that follows makes little sense without a prior glance at the paper.

“Deschamps estimated that without the reform, 21 men and 12 women would have been hired in the field of mathematics. But with the reform, committees whose membership met the quota hired 30 men and 3 women” Nature

Skipping the non-quantitative and somewhat ideological part of the report, as well as descriptive statistics, I looked mostly at the modelling behind the conclusions, as reported for instance in the above definite statement in Nature. Starting with a collection of assumptions and simplifications. A first dubious such assumption is that fields and even less universities where the more than 40% quota was already existing before (the 2015 reform) could be used as “control groups”, given the huge potential for confounders, especially the huge imbalance in female-to-male ratios in diverse fields. Second, the data only covers hiring histories for three French universities (out of 63 total) over the years 2009-2018 and furthermore merges assistant (Maître de Conférence) and full professors, where hiring is de facto much more involved, with often one candidate being contacted [prior to the official advertising of the position] by the department as an expression of interest (or the reverse). Third, the remark that

“there are no significant differences between the percentage of women who apply and those who are hired” (p.9)

seems to make the all discussion moot… and contradict both the conclusion and the above assertion! Fourth, the candidate’s qualification (or quality) is equated with the h-index, which is highly reductive and, once again, open to considerable biases in terms of seniority degree and of field. Depending on the publication lag and also the percentage of publications in English versus the vernacular in the given field. And the type of publications (from an average of 2.94 in business to 9.96 on physics]. Fifth, the report equates academic connections [that may bias the ranking] with having the supervisor present in the hiring committee [which sounds like a clear conflict of interest] or the candidate applying in the [same] university that delivered his or her PhD. Missing a myriad of other connections that make committee members often prone to impact the ranking by reporting facts from outside the application form.

“…controlling for field fixed effects and connections make the coefficient [of the percentage of women in the committee] statistically insignificant, though the point estimate remains high.” (p.17)

The models used by Pierre Deschamps are multivariate logit and probit regressions, where each jury attaches a utility to each of its candidates, made of a qualification term [for the position] and of a gender bias most surprisingly multiplying candidate gender and jury gender dummies. The qualification term is expressed as a [jury free] linear regression on covariates plus a jury fixed effect. Plus an error distributed as a Gumbel extreme variate that leads to a closed-form likelihood [and this seems to be the only reason for picking this highly skewed distribution]. The probit model is used to model the probability that one candidate has a better utility than another. The main issue with this modelling is the agglomeration of independence assumptions, as (i) candidates and hired ones are not independent, from being evaluated over several positions all at once, with earlier selections and rankings all public, to having to rank themselves all the positions where they are eligible, to possibly being co-authors of other candidates; (ii) jurys are not independent either, as the limited pool of external members, esp. in gender-imbalanced fields, means that the same faculty often ends up in several jurys at once and hence evaluates the same candidates as a result, plus decides on local ranking in connection with earlier rankings; (iii) independence between several jurys of the same university when this university may try to impose a certain if unofficial gender quota, a variate obviously impossible to fill . Plus again a unique modelling across disciplines. A side but not solely technical remark is that among the covariates used to predict ranking or first position for a female candidate, the percentage of female candidates appears, while being exogenous. Again, using a univariate probit to predict the probability that a candidate is ranked first ignores the comparison between a dozen candidates, both male and female, operated by the jury. Overall, I find little reason to give (significant) weight to the indicator that the president is a woman in the logistic regression and even less to believe that a better gender balance in the jurys has led to a worse gender balance in the hirings. From one model to the next the coefficients change from being significant to non-significant and, again, I find the definition of the control group fairly crude and unsatisfactory, if only because jurys move from one session to the next (and there is little reason to believe one field more gender biased than another, with everything else accounted for). And for another my own experience within hiring committees in Dauphine or elsewhere has never been one where the president strongly impacts the decision. If anything, the president is often more neutral (and never ever imoe makes use of the additional vote to break ties!)…

postdoctoral position in computational statistical physics and machine learning

Posted in Statistics with tags , , , , , , , , on February 12, 2019 by xi'an

permanent position for research on computational statistics and “omics” data

Posted in pictures, Statistics, Travel, University life with tags , , , , , , , , on February 4, 2019 by xi'an

There is an opening at the French agronomy and genetics research centre, INRA, for a permanent research position on the country campus of Joyu-en-Josas, south-west of Paris, with focus on computational statistics (incl. machine-learning) and collaborations on omics data. The deadline is March 4. (The procedure is somewhat involved, as detailed in the guide for candidates.) I want to stress this is a highly attractive position in terms of academic surroundings (research only campus, nearby Paris=Saclay and Orsay campuses), of location (Paris in the fields), and of status since permanent really means permanent!