Archive for books

p-values and decision-making [reposted]

Posted in Books, Statistics, University life with tags , , , , , , , , , , on August 30, 2017 by xi'an

In a letter to Significance about a review of Robert Matthews’s book, Chancing it, Nicholas Longford recalls a few basic facts about p-values and decision-making earlier made by Dennis Lindley in Making Decisions. Here are some excerpts, worth repeating in the light of the 0.005 proposal:

“A statement of significance based on a p-value is a verdict that is oblivious to consequences. In my view, this disqualifies hypothesis testing, and p-values with it, from making rational decisions. Of course, the p-value could be supplemented by considerations of these consequences, although this is rarely done in a transparent manner. However, the two-step procedure of calculating the p-value and then incorporating the consequences is unlikely to match in its integrity the single-stage procedure in which we compare the expected losses associated with the two contemplated options.”

“At present, [Lindley’s] decision-theoretical approach is difficult to implement in practice. This is not because of any computational complexity or some problematic assumptions, but because of our collective reluctance to inquire about the consequences – about our clients’ priorities, remits and value judgements. Instead, we promote a culture of “objective” analysis, epitomised by the 5% threshold in significance testing. It corresponds to a particular balance of consequences, which may or may not mirror our clients’ perspective.”

“The p-value and statistical significance are at best half-baked products in the process of making decisions, and a distraction at worst, because the ultimate conclusion of a statistical analysis should be a proposal for what to do next in our clients’ or our own research, business, production or some other agenda. Let’s reflect and admit how frequently we abuse hypothesis testing by adopting (sometimes by stealth) the null hypothesis when we fail to reject it, and therefore do so without any evidence to support it. How frequently we report, or are party to reporting, the results of hypothesis tests selectively. The problem is not with our failing to adhere to the convoluted strictures of a popular method, but with the method itself. In the 1950s, it was a great statistical invention, and its popularisation later on a great scientific success. Alas, decades later, it is rather out of date, like the steam engine. It is poorly suited to the demands of modern science, business, and society in general, in which the budget and pocketbook are important factors.”

Bacon in the Library [jatp]

Posted in Books, Kids, pictures, Travel, University life with tags , , , , , , , on May 23, 2017 by xi'an

packed off!!!

Posted in Books, pictures, R, Statistics with tags , , , , , , , , , , on February 9, 2013 by xi'an

La Défense, Paris, Feb. 04, 2013Deliverance!!! We have at last completed our book! Bayesian Essentials with R is off my desk! In a final nitty-gritty day of compiling and recompiling the R package bayess and the LaTeX file, we have reached versions that were in par with our expectations. The package has been submitted to CRAN (it has gone back and forth a few times, with requests to lower the computing time in the examples: each example should take less than 10s, then 5s…), then accepted by CRAN, incl. a Windows version, and the book has be sent to Springer-Verlag. This truly is a deliverance for me as this book project has been on my work horizon almost constantly for more than the past two years, led to exciting times in Luminy, Carnon and Berlin, has taken an heavy toll on my collaborations and research activities, and was slowly turning into a unsavoury chore! I am thus delighted Jean-Michel and I managed to close the door before any disastrous consequence on either the book or our friendship could develop. Bayesian Essentials with R is certainly an improvement compared with Bayesian Core, primarily by providing a direct access to the R code. We dearly hope it will attract a wider readership by reducing the mathematical requirements (even though some parts are still too involved for most undergraduates) and we will keep testing it with our own students in Montpellier and Paris over the coming months. In the meanwhile, I just enjoy this feeling of renewed freedom!!!

Robert Louis Balfour Stevenson

Posted in Books, pictures, Travel with tags , , , , , on February 8, 2013 by xi'an

IMG_4770

author rank

Posted in Statistics with tags , , , , , on October 11, 2012 by xi'an

Got the following email from Amazon:

Today we have added a new feature, Amazon Author Rank, the definitive list of best-selling authors on Amazon.com. This list makes it easy for readers to discover the best-selling authors on Amazon.com overall and within a selection of major genres. Your Amazon Author Rank is 44,881 in Print Books.

It is a new feature so, with a very limited past horizon, this rank seems to be moving wildly! (For instance, it is now 36,776, just a few hours later.) But so are the individual book sales. Hence a clear lack of smoothing in the indicator.

Another interesting feature of this Author Central facility is the display of US sales by district, Not only because it shows that New York and San Francisco are the cities where I sell the most books (great!) but also because it uses the notion of “combined areas”, aggregating “the copies sold in these sparsely populated areas in order to obscure any single retailer’s sales”. A good display of data protection (even though the level of aggregation sounds too high to me, resulting in “combined areas” being the 3rd highest sale area. And including Gainesville, Florida and Ithaca, New York, the two latest locations of George Casella, in this combination!