Archive for La Recherche

Truly random [again]

Posted in Books, R, Statistics, University life with tags , , , , , , , , on December 10, 2010 by xi'an

“The measurement outputs contain at the 99% confidence level 42 new random bits. This is a much stronger statement than passing or not passing statistical tests, which merely indicate that no obvious non-random patterns are present.” arXiv:0911.3427

As often, I bought La Recherche in the station newsagent for the wrong reason! The cover of the December issue was about “God and Science” and I thought this issue would bring some interesting and deep arguments in connection with my math and realism post. The debate is very short, does not go in any depth. reproduces the Hawking’s quote that started the earlier post, and recycles the same graph about cosmology I used last summer in Vancouver! However, there are alternative interesting entries about probabilistic proof checking in Mathematics and truly random numbers… The first part is on an ACM paper on the PCP theorem by Irit Dinur, but is too terse as is (while the theory behind presumably escapes my abilities!). The second part is about a paper in Nature published by Pironio et al. and arXived as well. It is entitled “Random numbers certified by Bell’s Theorem” and also is one of the laureates of the La Recherche prize this year. I was first annoyed by the French coverage of the paper, mentioning that “a number was random with a probability of 99%” (?!) and that “a sequence of numbers is  perfectly random” (re-?!). The original paper is however stating the same thing, hence stressing the different meaning associated to randomness by those physicists, “the unpredictable character of the outcomes” and “universally-composable security”. The above “probability of randomness” is actually a p-value (associated with the null hypothesis that Bell’s inequality is not violated) that is equal to 0.00077. (So the above quote is somehow paradoxical!) The huge apparatus used to produce those random events is not very efficient: on average, 7 binary random numbers are detected per hour… A far cry from the “truly random” generator produced by Intel!

Ps-As a concidence, Julien Cornebise pointed out to me that there is a supplement in the journal about “Le Savoir du Corps” which is in fact handled by the pharmaceutical company Servier, currently under investigation for its drug Mediator… A very annoying breach of basic journalistic ethics in my opinion!

Truly random?!

Posted in Books, R, Statistics, University life with tags , , , , , , , on September 7, 2010 by xi'an

Having purchased the September edition of La Recherche because of its (disappointing!) coverage on black matter, I came by a short coverage on an Intel circuit producing “truly random” numbers… I already discussed this issue in an earlier post, namely that there is no reason physical generators are “more” random than congruential pseudo-random generators, but this short paper repeats the same misunderstanding on the role of “random” generators. The paper mentions dangers of pseudo-random generators for cryptography (but this is only when you know the deterministic function and the sequence of seeds used so far), while it misses the essential aspect of valid generators, namely that their distribution is exactly known (e.g., uniform) and, in the case of parallel generations, which seems to be the case for this circuit, that the generators are completely independent. La Recherche mentions that the entropy of the generator is really high, but this is more worrying than reassuring, as the Intel engineers do not have a more elaborate way to prove uniformity than a Monte Carlo experiment…

There is actually a deeper entry found on Technology Review. (Which may have been the source for the paper in the technology tribune of La Recherche.) The article mentions that the generator satisfied all benchmarks of “randomness” maintained by NIST. Those statistical tests sound much more reassuring than the entropy check mentioned by La Recherche, as they essentially reproduce Marsaglia’s DieHard benchmark… I remain rather skeptical about physical devices, as compared with mathematical functions, because of (a) non-reproducibility which is a negative feature despite what the paper says and of (b) instability of the device, which means that proven uniformity at time t does not induce uniformity at time t+1. Nonetheless, if the gains in execution are gigantic, it may be worth the approximation for most applications. But please stop using “true” in conjunction with randomness!!!

La Recherche on current mathematics

Posted in Books, Statistics, University life with tags , , , on November 28, 2009 by xi'an

“Perrette asked why statistics did not have a category, and Mr Ruche said  he had decided that, as statistics dealt with specifics, it was too empirical to be a section of maths.” Denis Guedj, The Parrot’s Theorem

In November, La Recherche (also) published a special issue on the power of mathematics. While this issue contains a load of interesting papers on the various facets of current mathematics, some of which being edited reprints of earlier papers, and includes a good interview of Wendelin Werner, I find it quite significant that none of those papers ever mentions statistics! It sounds as if statistics was not part of mathematics for the editors of this issue, especially when considering the section on the applications of mathematics that includes character recognition and computer intensive methods. I understand that Gödel’s theorem and the theory of proofs may be more appealing to the layman than machine learning or bootstrap, but I still resent this exclusion from the mathematical “pantheon”! (Ironically, or not!, one of the few statistics books included in the bibliography is Py’s “Statistiques sans formules mathematiques“!) This reminds me of the exclusion of statistics from the field of mathematics by the writer/journalist Denis Guedj in his otherwise captivating The Parrot’s Theorem!

Bad graph of the day

Posted in Books, Statistics with tags , , , on October 30, 2009 by xi'an

Another meaningless graph found in the November issue of La Recherche: a histogram of the predictions of the World population by 2005 attached to a brief discussion of the challenges of providing food for this population. No mention is made of the source(s) for this absurd agglomerate of predictions, (could I add mine as well?!) while the discussion picks the median prediction for its reference number: as if Science was run by majority rule… As an unflattering coincidence (for La Recherche!), the other French monthly popular science magazine Pour la Science has simultaneously published a rather well-argumented special issue on randomness (by Jaroslaw Strzalko, Juliusz Grabski and Tomasz Kapitaniak who are Polish physicists), refering to one recent paper by Persi Diaconis on the randomness of coin tosses. Being associated with Scientific American certainly helps in producing quality papers! (There is also a paper by Ivar Ekeland in the same issue, as well as the paper by Andrew Gelman already signaled.)

“Pour la Science” almost goes Bayesian!

Posted in Books, Statistics with tags , , , , on October 22, 2009 by xi'an

After the strange views held on Bayesian statistics by the popular science magazine La Recherche, it is  more than comforting to see the other popular science magazine Pour la Science to publish a more balanced paper on the role of statistical evidence, both frequentist and Bayesian. And by Andrew Gelman! This paper is actually a translation into French of a paper of Andrew with David Wiekliem, published earlier in American Scientist. I can only make one complaint about a missing reference to Laplace (the true father of Bayesian statistics!) who did study the difference between male and female births in his Théorie Analytique des Probabilités.

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