Archive for survey sampling

coronavirus counts do not count

Posted in Books, pictures, Statistics with tags , , , , , , , , on April 8, 2020 by xi'an

Somewhat by chance I came across Nate Silver‘s tribune on FiveThirtyEight about the meaninglessness of COVID-19 case counts. As it reflects on sampling efforts and available resources rather than actual cases, furthermore sampling efforts from at least a fortnight.

“The data, at best, is highly incomplete, and often the tip of the iceberg for much larger problems. And data on tests and the number of reported cases is highly nonrandom. In many parts of the world today, health authorities are still trying to triage the situation with a limited number of tests available. Their goal in testing is often to allocate scarce medical care to the patients who most need it — rather than to create a comprehensive dataset for epidemiologists and statisticians to study.”

This article runs four different scenarios, with the same actual parameters for the epidemics, and highly different and mostly misleading perceptions based on the testing strategies. This is a highly relevant warning but I am surprised Nate Silver does not move to the rather obvious conclusion that some form of official survey or another, for instance based on capture-recapture and representative samples, testing for present and past infections, should be implemented on a very regular basis, even with a limited number of tested persons to get a much more reliable vision of the status of the epidemics. Here, the French official institute of statistics, INSEE, would be most suited to implement such a scheme.

Nature tidbits

Posted in Books, Statistics, University life with tags , , , , , , , , , , , on September 18, 2018 by xi'an

In the Nature issue of July 19 that I read in the plane to Singapore, there was a whole lot of interesting entries, from various calls expressing deep concern about the anti-scientific stance of the Trump administration, like cutting funds for environmental regulation and restricting freedom of communication (ETA) or naming a non-scientist at the head of NASA and other agencies, or again restricting the protection of species, to a testimony of an Argentinian biologist in front of a congressional committee about the legalisation of abortion (which failed at the level of the Agentinian senate later this month), to a DNA-like version of neural network, to Louis Chen from NUS being mentioned in a career article about the importance of planning well in advance one’s retirement to preserve academia links and manage a new position or even career. Which is what happened to Louis as he stayed head of NUS after the mandatory retirement age and is now emeritus and still engaged into research. (The article made me wonder however how the cases therein had be selected.) It is actually most revealing to see how different countries approach the question of retirements of academics: in France, for instance, one is essentially forced to retire and, while there exist emeritus positions, it is extremely difficult to find funding.

“Louis Chen was technically meant to retire in 2005. The mathematician at the National University of Singapore was turning 65, the university’s official retirement age. But he was only five years into his tenure as director of the university’s new Institute for Mathematical Sciences, and the university wanted him to stay on. So he remained for seven more years, stepping down in 2012. Over the next 18 months, he travelled and had knee surgery, before returning in summer 2014 to teach graduate courses for a year.”

And [yet] another piece on the biases of AIs. Reproducing earlier papers discussed here, with one obvious reason being that the learning corpus is not representative of the whole population, maybe survey sampling should become compulsory in machine learning training degrees. And yet another piece on why protectionism is (also) bad for the environment.

foie gras fois trois

Posted in Statistics, Wines with tags , , , , , , on December 31, 2014 by xi'an

As New Year’s Eve celebrations are getting quite near, newspapers once again focus on related issues, from the shortage of truffles, to the size of champagne bubbles, to the prohibition of foie gras. Today, I noticed an headline in Le Monde about a “huge increase in French people against force-fed geese and ducks: 3% more than last year are opposed to this practice”. Now, looking at the figures, it is based on a survey of 1,032 adults, out of which 47% were against. From a purely statistical perspective, this is not highly significant since


is compatible with the null hypothesis N(0,1) distribution.


Posted in Statistics, Travel, University life with tags , , , , , on August 8, 2010 by xi'an

6831250-3x2-700x467The first trans-Atlantic edition of Significance contains a paper by Kerrie Mengersen on her recent work in the jungles of Borneo, analysing a survey among villagers about the populations of orangutans and the evolution patterns of those populations. I knew Kerrie was involved in this study in the past years, but it is nice to seecover the outcome in such a clear format. I am looking forward the technical aspects of the spatial analysis that allows for a better understanding of the population patterns and of their dynamics. (The title of the paper is great as well: “The sound of silence: listening to the villagers to learn about orangutans”.)

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