Archive for amazon associates

haunting of tramcar 105 [book review]

Posted in Statistics with tags , , , , , , , , , , , on April 20, 2019 by xi'an

A mix of steampunk and urban magic in a enlightened 1912 Cairo sounded like a good prolegomena and I bought P. Djèli Clark’s The haunting of tram car 015 on this basis. As it happens, this is actually a novella of 123 pages building on the same universe as a previous work of the author, A dead djinn in Cairo, which however is even shorter and only available as a Kindle book… I really enjoyed the short read and its description of an alternate Cairo that is competing with Paris and London, thanks to the advantage brought by the supernatural powers of djinns. (And apparently also gaining the independence Egypt could not secure under the British protectorate.) The English suffragettes have also their counterparts in Egypt and the country is about to decide about women right to vote. The story itself is nice if not stratospheric, with mostly well-drawn characters and good dialogues. (The core of the plot relies on smuggling sweets from Armenia, though, a rather weak link.) As in an earlier order, the book itself was not properly printed, with a vertical white band of erased characters on most odd pages, presumably another illustration of the shortcomings of the  print-on-demand principle. (Which means that I sent the book back to Amazon rather than leaving it in the common room.)

look, look, confidence! [book review]

Posted in Books, Statistics, University life with tags , , , , , , , , , , , , , , , , on April 23, 2018 by xi'an

As it happens, I recently bought [with Amazon Associate earnings] a (used) copy of Confidence, Likelihood, Probability (Statistical Inference with Confidence Distributions), by Tore Schweder and Nils Hjort, to try to understand this confusing notion of confidence distributions. (And hence did not get the book from CUP or anyone else towards purposely writing a review. Or a ½-review like the one below.)

“Fisher squared the circle and obtained a posterior without a prior.” (p.419)

Now that I have gone through a few chapters, I am no less confused about the point of this notion. Which seems to rely on the availability of confidence intervals. Exact or asymptotic ones. The authors plainly recognise (p.61) that a confidence distribution is neither a posterior distribution nor a fiducial distribution, hence cutting off any possible Bayesian usage of the approach. Which seems right in that there is no coherence behind the construct, meaning for instance there is no joint distribution corresponding to the resulting marginals. Or even a specific dominating measure in the parameter space. (Always go looking for the dominating measure!) As usual with frequentist procedures, there is always a feeling of arbitrariness in the resolution, as for instance in the Neyman-Scott problem (p.112) where the profile likelihood and the deviance do not work, but considering directly the distribution of the (inconsistent) MLE of the variance “saves the day”, which sounds a bit like starting from the solution. Another statistical freak, the Fieller-Creasy problem (p.116) remains a freak in this context as it does not seem to allow for a confidence distribution. I also notice an ambivalence in the discourse of the authors of this book, namely that while they claim confidence distributions are both outside a probabilisation of the parameter and inside, “producing distributions for parameters of interest given the data (…) with fewer philosophical and interpretational obstacles” (p.428).

“Bias is particularly difficult to discuss for Bayesian methods, and seems not to be a worry for most Bayesian statisticians.” (p.10)

The discussions as to whether or not confidence distributions form a synthesis of Bayesianism and frequentism always fall short from being convincing, the choice of (or the dependence on) a prior distribution appearing to the authors as a failure of the former approach. Or unnecessarily complicated when there are nuisance parameters. Apparently missing on the (high) degree of subjectivity involved in creating the confidence procedures. Chapter 1 contains a section on “Why not go Bayesian?” that starts from Chris Sims‘ Nobel Lecture on the appeal of Bayesian methods and goes [softly] rampaging through each item. One point (3) is recurrent in many criticisms of B and I always wonder whether or not it is tongue-in-cheek-y… Namely the fact that parameters of a model are rarely if ever stochastic. This is a misrepresentation of the use of prior and posterior distributions [which are in fact] as summaries of information cum uncertainty. About a true fixed parameter. Refusing as does the book to endow posteriors with an epistemic meaning (except for “Bayesian of the Lindley breed” (p.419) is thus most curious. (The debate is repeating in the final(e) chapter as “why the world need not be Bayesian after all”.)

“To obtain frequentist unbiasedness, the Bayesian will have to choose her prior with unbiasedness in mind. Is she then a Bayesian?” (p.430)

A general puzzling feature of the book is that notions are not always immediately defined, but rather discussed and illustrated first. As for instance for the central notion of fiducial probability (Section 1.7, then Chapter 6), maybe because Fisher himself did not have a general principle to advance. The construction of a confidence distribution most often keeps a measure of mystery (and arbitrariness), outside the rather stylised setting of exponential families and sufficient (conditionally so) statistics. (Incidentally, our 2012 ABC survey is [kindly] quoted in relation with approximate sufficiency (p.180), while it does not sound particularly related to this part of the book. Now, is there an ABC version of confidence distributions? Or an ABC derivation?) This is not to imply that the book is uninteresting!, as I found reading it quite entertaining, with many humorous and tongue-in-cheek remarks, like “From Fraser (1961a) and until Fraser (2011), and hopefully even further” (p.92), and great datasets. (Including one entitled Pornoscope, which is about drosophilia mating.) And also datasets with lesser greatness, like the 3000 mink whales that were killed for Example 8.5, where the authors if not the whales “are saved by a large and informative dataset”… (Whaling is a recurrent [national?] theme throughout the book, along with sport statistics usually involving Norway!)

Miscellanea: The interest of the authors in the topic is credited to bowhead whales, more precisely to Adrian Raftery’s geometric merging (or melding) of two priors and to the resulting Borel paradox (xiii). Proposal that I remember Adrian presenting in Luminy, presumably in 1994. Or maybe in Aussois the year after. The book also repeats Don Fraser’s notion that the likelihood is a sufficient statistic, a point that still bothers me. (On the side, I realised while reading Confidence, &tc., that ABC cannot comply with the likelihood principle.) To end up on a French nitpicking note (!), Quenouille is typ(o)ed Quenoille in the main text, the references and the index. (Blame the .bib file!)

kingdoms of dust [book review]

Posted in Books, Kids with tags , , , , , , on May 13, 2017 by xi'an

Kingdoms of Dust is the third (and last?) book in the Isyllt Iskaldur (Necromancer) series, written by Amanda Downum. I had enjoyed very much the previous two volumes and was not aware of the existence of a third one, existence I only realised a few weeks ago when I prepared a bulk amazon associate ordering for my trip to Harvard. While being reunited with several characters from the previous books made reading Kingdoms of Dust definitely enjoyable, I found the plot too dry [no pun intended!] and the civilisation exposed through the story fairly caricaturesque, an almost Disneyesque Arabian universe whose economics remain unspecified. Which seems to happen a lot these days with the theme of warrior desert tribes with proto-Muslim religion(s) taking a share of the fantasy literature (as in the Demon Cycle and the Godspeaker trilogy). What I appreciated more was the psychological evolution of the main character Iskaldur from depression to an almost Christ-esque role, liberating most of the other major characters in the story. And the feature that somewhow there was no superlatively evil enemy to defeat, but a conjunction of ill-timed events to unravel.

humanitarian project in Madagascar

Posted in Books, Kids, pictures, Travel, University life with tags , , , , , , , , , on March 15, 2017 by xi'an

As the budget of the humanitarian trip to Madagascar our daughter organises with other students of the Paris-Sud Medical School next summer is still short of several thousand euros, I repost the call for support I made a few months ago.

Their project is called Mada Tsatsaka, mada for Madagascar and tsatsaka for a local lizard. The team plans to bring basic drugs and educational material and to work in a dispensary, an orphanage, as well as a shelter for women victims of violence. (More below!)

I thus bring this project to the ‘Og’s readers’ attention in case they wish to support. The best approach is use this web site for donations (in English) to Evadeh Mada Tsatsaka. (Evadeh is the mother association for all humanitarian projects in the medical school.) A free-of-charge (!) alternative is to shop on amazon.com following this associate link as I vouch to transfer all my associate gains in the next four months to the project.

Upon request, more details on the project:

  • 2 weeks in Maventibao working in a clinic : Mada Clinics, helping two nurses with free medical examinations and providing extra medical equipment and drugs. And also helping with drinking water improvement. The team further hopes to help with the purchase of a car associated with the clinic and linking with the hospital in  Diego (4h away) and with hiring a doctor in the nearby clinic of Amboangamamy.
  • 2 weeks in an orphanage in Antananarivo, Ankanifitahiana, in collaboration with BLOC Léo Madagascar, helping in financing and installing a library and a music room, and participating in classes and games with the children. Depending on the funding, the team would also like to help with installing a solar oven.

Mada Tsatsaka

Posted in Books, Kids, pictures, Travel, University life with tags , , , , , , , on December 17, 2016 by xi'an

Along with other students of the Paris-Sud Medical School, our daughter is planning a humanitarian trip to Madagascar next summer, following a long-term tradition in her school with groups sent to Madagascar as well as Vietnam, Peru and Nepal. The project is called Mada Tsatsaka, mada for Madagascar and tsatsaka for a local lizard. They plan to bring basic drugs and educational material and to work in a dispensary, an orphanage, as well as a shelter for women victims of violence. They have been now working for several months at meeting the budget for this project, from selling pies and quiches on local markets (I helped with the quiches!) to wrapping gifts at supermakets all around, to engaging local authorities and charities, but are still far from reaching this goal.

I thus bring this project to the ‘Og’s readers’ attention in case they wish to support. The best approach is use this donation form (in English) for Evadeh Mada Tsatsaka. A free of charge (!) alternative is to shop on amazon.com following this associate link as I vouch to transfer all my associate gains in the next six months to the project.

Amazonish warning

Posted in Books, Kids, R, Statistics with tags , , , , , on March 11, 2016 by xi'an

As in previous years, I want to repost a warning to ‘Og readers that all http links to Amazon.com [and much more rarely to Amazon.fr] products found on this ‘Og are actually susceptible to reward me with an advertising percentage if a purchase is made by the reader in the 24 hours following the entry on Amazon through this link, thanks to the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to amazon.com/fr. Here are some of the most Og-unrelated purchases, less exotic than in previous years (maybe because of a lower number of items):

Once again, books I reviewed, positively or negatively, were among the top purchases… Like a dozen Monte Carlo simulation and resampling methods for social science, half a dozen Statistics done wrong, and Think Bayes: Bayesian Statistics Made Simple [which also attracted a lot of visits when I reviewed it], and still a few copies of Naked Statistics (despite a most critical review.) Thanks to all readers activating those links and feeding further my book addiction, with the drawback of inducing even more book reviews on the ‘Og…