It took me a while to get Nate Silver’s the signal and the noise: why so many predictions fall – but some don’t (hereafter s&n) and another while to read it (blame A Memory of Light!).
“Bayes and Price are telling Hume, don’t blame nature because you are too daft to understand it.” s&n, p.242
I find s&n highly interesting and it is rather refreshing to see the Bayesian approach so passionately promoted by a former poker player, as betting and Dutch book arguments have often been used as argument in favour of this approach. While it works well for some illustrations in the book, like poker and the stock market, as well as political polls and sports, I prefer more decision theoretic motivations for topics like weather prediction, sudden epidemics, global warming or terrorism. Of course, this passionate aspect makes s&n open to criticisms, like this one by Marcus and Davies in The New Yorker about seeing everything through the Bayesian lenses. The chapter on Bayes and Bayes’ theorem (Chapter 8) is a wee caricaturesque in this regard. Indeed, Silver sees too much in Bayes’ Essay, to the point of mistakenly attributing to Bayes a discussion of Hume’s sunrise problem. (The only remark is made in the Appendix, which was written by Price—like possibly the whole of the Essay!—, and P.S. Laplace is the one who applied Bayesian reasoning to the problem, leading to Laplace’s succession rule.) The criticisms of frequentism are also slightly over-the-levee: they are mostly directed at inadequate models that a Bayesian analysis would similarly process in the wrong way. (Some critics argue on the opposite that Bayesian analysis is too much dependent on the model being “right”! Or on the availability of a fully-specified model.) Seeing frequentism as restricted to “collecting data among just a sample of the population rather than the whole population” (p.252) is certainly not presenting a broad coverage of frequentism.
“Prediction serves a very central role in hypothesis testing, for instance, and therefore in all of science.” s&n, p.230
The book is written in a fairly enjoyable style, highly personal (no harm with that) and apart from superlativising (!) everyone making a relevant appearance—which seems the highest common denominator of all those pop’sci’ books I end up reviewing so very often!, maybe this is something like Rule #1 in Scientific Writing 101 courses: “makes the scientists sound real, turn’em into real people”—, I find it rather well-organised as it brings the reader from facts (prediction usually does poorly) to the possibility of higher quality prediction (by acknowledging prior information, accepting uncertainty, using all items of information available, further accepting uncertainty, &tc.). I am not sure the reader is the wiser by the end of the book on how one should improve one’s prediction tools, but there is a least a warning about the low quality of most predictions and predictive tools that should linger in the reader’s ears…. I enjoyed very much the chapter on chess, esp. the core about Kasparov’s misreading the computer reasons for a poor move (no further spoiler!), although I felt it was not much connected to the rest of the book.
In his review, Larry Wasserman argues that the defence Silver makes of his procedure is more frequentist than Bayesian. Because he uses calibration and long-term performances. Well… Having good calibration properties does not mean the procedure is not Bayesian or frequentist, simply that it is making efficient use of the available information. Anyway, I agree (!) with Larry on the point that Silver somehow “confuses “Bayesian inference” with “using Bayes’ theorem”. Or puts too much meaning in the use of Bayes’ theorem, not unlike the editors of Science & Vie a few months ago. To push Larry’s controversial statement a wee further, I would even wonder whether the book has anything to do about inference. Indeed, in the end, I find s&n rather uninformative about statistical modelling and even more (or less!) about model checking. The only “statistical” model that is truly discussed over the book is the power law distribution, applied to earthquakes and terrorist attack fatalities. This is not an helpful model in that (a) it does not explain anything, as it does not make use of covariates or side information, and (b) it has no predictive power, especially in the tails. On the first point, concluding that Israel’s approach to counter-terrorism is successful because it “is the only country that has been able to bend” the power-law curve (p.442) sounds rather hasty. I’d like to see the same picture for Iraq, say. Actually, I found one in this arXiv paper. And it looks about the same for Afghanistan (Fig.4). On the second point, the modelling is poor in handling extreme values (which are the ones of interest in both cases) and cannot face change-points or lacks of stationary, an issue not sufficiently covered in s&n in my opinion. The difficulty with modelling volatile concepts like the stock market, the next presidential election or the move of your poker opponents is that there is no physical, immutable, law at play. Things can change from one instant to the next. Unpredictably. Esp. in the tails.
There are plenty of graphs in s&n, which is great, but not all of them are at the Tufte quality level. For instance, Figure 11-1 about the “average time U.S. common stock was held” contains six pie charts corresponding to six decades with the average time and a percentage which could be how long compared with the 1950s a stock was held. The graph is not mentioned in the text. (I will not mention Figure 8-2!) I also spotted a minuscule typo (`probabalistic’) on Figure 10-2A.
Maybe one last and highly personal remark about the chapter on poker (feel free to skip!): while I am a very poor card player, I do not mind playing cards (and loosing) with my kids. However, I simply do not understand the rationale of playing poker. If there is no money at stake, the game does not seem to make sense since every player can keep bluffing until the end of time. And if there is money at stake, I find the whole notion unethical. This is a zero sum game, so money comes from someone else’s pocket (or more likely someone else’s retirement plan or someone else’s kids college savings plan). Not much difference with the way the stock market behaves nowadays… (Incidentally, this chapter did not discuss at all the performances of computer poker programs, unexpectedly, as the number of possibilities is very small and they should thus be fairly efficient.)
Arnaldur Indriðason’s Outrage (Myrká in Icelandic) is a thriller in the Erlandur series, where inspector Erlundur does not appear at all but is replaced with inspector Elinborg who deals with the murder of a drug rapist. And her family problems. The book got a prize in France and its focus on women issues makes it more interesting than the polce story itself, which meanders quite a lot and relies on too many coincidences. But I do like the stuffing no-exit (huis clos) atmosphere. (The above image is the critique in French from Le Canard Enchaîné.) Given that Erlundur has disappeared, this book stands in between other Indriðason’s books, Hypothermia (Harðskafi) and Black Skies (Svörtuloft).
I had mentioned my uneasiness about Hoffman’s The Left Hand of God a few months ago, both because of a very uneven style, a plot borrowing so much to real events and locations, and a highly ambiguous central character. I nonetheless read the second tome, The Last Four Things, following a request from my son. My impression has definitely not improved, mostly again for a high rate of borrowing from existing facts and places (like Chartres used for the papal seat). The title itself is found in many books and comes from a painting by Bosch I missed in Madrid last time I visited El Prado. The characters are mostly the same ones as in The Left Hand of God and they remain shallow and unconvincing. The political plot(s) are of no interest whatsoever. The reunion between Cale and Arbell is botched, to say the least. (And still some people love it!)
mew… In line with the recent chronicles in the series, the book is not worth any level of recommendation. The plots get thinner and thinner, the dialogues and settings less and less realistic for their 14th Century environment, and the resolution is rushed with no even a pretence of disguise for the massive infodump in the Epilogue! It feels like I have already seen it all in previous books: the trip away from Cambridge to gather an uncertain inheritance, the flow of new characters taking an unreasonable interest in Michelhouse affairs, an endless sequence of deaths, poisons, “wanton” nuns, attractive women turning into insane murderesses, fights for life in an abandoned and crumbling church, &tc. Among the many implausible facts in the current volume, the vicar-chorals’ obsession with shoes, speaking of “intelligent, liberal people” as in a 21st Century society, or hiring an actor to play the role of a (long dead) priest for more than a month… I will for certain abstain from buying the incoming 18th chronicle, appropriately planned for April the 1st!
When ordering books from amazon.fr for my daughter, I added Ascension, a manga by Shin’ichi Sakamoto about climbing. I was however quite disappointed by the result, both for the silly plot and for the lack of realism in its climbing connection!
