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(surname at math dot leidenuniv dot nl), or mobile phone.
Click here for my postal and visiting addresses,
mobile phone number, various other email addresses and other contact possibilities.
In particular, I have just started a one man statistical consultation business
Combray Causality Consulting.
I have revised and extended my farewell lecture "From killer nurses to quantum entanglement"", and am slowly converting it into a paper on the Ben Geen case with amazing new statistical graphics. Latest version: 3 December 2019. Skip the few well-labelled pages on quantum entanglement if you are only interested in innocent convicted serial killer nurses. See also my new Ben Geen talk. Here are links to the expert opinion of Jane Hutton and the expert opinion of Professor David Denison (who sadly died in 2014) at Ben's appeal in 2009 concerning the statistical, or rather scientific issues, around "unexpected clusters of medical cases" and their association with particular health care workers. The judge did not allow Jane to summarise het "Opinion" (technical term for an expert's report) in court in person because it was "merely common sense", as was also Denison's Opinion. At the judge's summing up, the jurors were also instructed to ignore that evidence. No common sense in my court! (shades of Sally Clark: it was "not rocket science"). English courts are also forbidden to use Bayes' theorem.
I'm a member of the North Sea Group, a circle of scholars and scientists mainly from countries around the North Sea, interested in legal evidence and legal proof. We have a webpage with blog and forum. I'm webmaster. The group has been meeting at annual workshops already for several years. A speciality is to study specific cases in depth using different methodologies from computer science and artificial intelligence, from psychology, philosophy and law, from statistics and probability. You can guess what cases I am contributing!
Lecture course "The Role of Statistical Science in Quantum Information" to be given at Fudan University, Shanghai, and Peking University, Beijing, September/October 2019.
Illustrations: the satellite Micius was used in Jianwei Pan's Earth (Shanghai) - Space (Micius) - Earth (Beijing) quantum key-distribution experiment in 2017. Here are a links to directories containing materials for my courses at Fudan University and at Peking University. The Fudan course is finished now but the course materials need correction and a "user's guide". I'm presently half-way preparing the Peking course.
Foraging for wild mushrooms.
The intersection axiom of conditional independence.
Dutch New Herring, correlation vs causation, and furthering good scientific research practices.
It is getting hard to find the two Tilburg University press releases and economist Ben Vollaard's two "AD Haringtest" papers on internet, so here are links: AD Haringtest paper July 2017, AD Haringtest update November 2017, Press Release July 2017, Press Release November 2017.
I will put the links into the slides, as well as update with my latest research findings on time-dependence through self-selection of participants and panel: the "samples" are not random samples. Conflict of interest - I was asked for my scientific opinion on the original papers by one of the parties in the ensuing legal case. Sorry, the original documents here are all in Dutch, and the two data sets are not available at this moment.
26 August, 2015. They did it at last! A first reaction.
What did they do, exactly, and what was my (modest) scientific
Illustrations: Figure 7 from "Bertlmann's socks and the nature of reality", Bell (1981); and the set-up in Delft, 2015.
See "Bell games" for a comparison of the standard Bell experiment and the Delft "event-ready detectors" version built on top of entanglement swapping.
Interview with John Bell (OMNI, 1988)
Quantum Love (Delft YouTube video
I was asked by defense lawyers
working on behalf of Ben Geen, to analyse statistical data of
occurrence of respiratory arrest in accident and emergency at numerous
(draft R html notebook,
After I had done my statistical work, I dug more deeply into
other aspects of the case. The more I discovered, the more I was shocked that
this case was a carbon copy of our own (Netherlands) case of Lucia de Berk.
However there are three important differences. (1) The UK media did an even more
perfect hatchet job on him than the Dutch media did on Lucia. (2) The Criminal Cases
Review Commission is understaffed and underfunded, and takes a formalistic (legalist)
view: give us a "new legal fact" or we will do nothing. (3) There is no Metta de Noo:
no medical whistleblower. In the Lucia case, Metta de Noo fought for 7 years to get
Lucia the fair (re-) trial which Lucia deserved. Metta is a senior medical expert,
well connected in society, and she had inside information about the case.
In the Lucia case, what was needed (and finally happened at the re-trial in Arnhem,
2009--2010) was an independent and thorough re-appraisal of
existing (medical) evidence.
Ben has by now sat out about 12 years of his 30 year sentence. Because he claims to be innocent he is denied any "good prisoner" benefits and will also never get parole or early release. A small supporters' group set up a website Justice for Ben Geen.
Some UK journalists, at "The Times" no less, briefly showed some interest: Nurse 'was victim of Shipman hysteria' But recently his case is forgotten again.
Some years ago I offered a prize for the person who remasters the logo of the VVS: the Dutch statistical society (top image) in the most beautiful postscript. An exercise in curve fitting with splines, perhaps? Better still would be a mathematical/statistical story of the curves themselves, providing an elegant parametric family which reproduces the whole logo. Finally I decided to do it myself, and I think I am getting close with this perspective image of some very simple 3-dimensional curves, with indeed a statistical story behind them (bottom). The R script which draws this logo can be found here. It should generate a rotatable 3-d image...
See the slides of my Amst-R-dam R users group meetup 2011 (updated 2012) talk R-fun: part 1, the VVS logo in R; part 2, R on an iDevice. For some old news on "R on an iDevice" see the 2014 talk R on an iDevice, given at a Data Science NL meetup.
For more R fun: I am nowadays an enthusiastic user of RStudio and RPubs. You can find all kinds of R work by me at my RPubs site.
VVS stands for "Vereniging voor Statistiek". SMS stands for "Section Mathematical Statistics". The VVS also has an OR section, hence the common alternative name VVS-OR. And nowadays the society has a nice new logo, though it doesn't look to me so much like anything to do with statistics
I must admit to getting a lot of fun (and scientific stimulation) from interacting with Bell-deniers. More generally I consider this an important part of science-outreach: how can we explain Bell's theorem to the general public? Well, a good start is to try to understand the mentality of very smart and well-educated people who believe that Bell made some fundamental but simple mistake, that they have exposed that mistake, and that there is an establishment conspiracy to suppress their findings. 7 years ago, I wrote a tutorial paper intended to clarify the situation around the Joy Christian model. Since some of his work actually got published in decent journals in recent years, I have updated, expanded, and submitted my analysis of them to a journal myself. After quite a few struggles, I managed to get it also accepted by arXiv moderators: Does Geometric Algebra provide a loophole to Bell’s Theorem? These activities also led in (2015) to short papers in the Springer journal IJTP (International Journal of Theoretical Physics) and the Elsevier journal RinP (Results in Physics), refuting results in papers by J. Christian and by H. Geurdes which had appeared in those journals in the same year. I hope someone finds them useful. My "victims" were not amused, I'm sorry for that. I analyse and criticise their work, not their persons.
The master specialization Statistical
Science for the Life and Behavioural Sciences is a collaboration of our group with
others in biomedical statistics, biostatistics, and psychometrics.
Here you can find links to various courses I have given in the past, in particular quantum statistics, statistics for astronomers, HOVO courses (adult education courses, in Dutch) on use and abuse of statistics, forensic science (Hovo-criminalistiek-statistiek-1, Hovo-criminalistiek-statistiek-2, Hovo-criminalistiek-statistiek-3).
WARNING: Richard P. Feynmann said that attempting to understand quantum mechanics causes you to fall into a black hole, never to be heard from again
The past is particles, the future is a wave
Bell's fifth position
First Leiden inaugural lecture
Past phd students
Just for fun: things you wish your computer had (including the classic clippy's suicide note)
A few years ago I discovered the enormous disussion on the Monty Hall (three doors) problem on wikipedia. My published writings on the subject are, in order of writing (and in order of insightfulness)an invited contribution to Springer's International Encyclopaedia of Statistical Science, 2010, a paper in Statistica Neerlandica, 2011, and contributions to the peer reviewed internet encyclopedias citizendium.org and StatProb.com. In this manuscript you will find an expanded version the most recent published work, the StatProb.com article.
Suppose the car is hidden behind one of the three
doors by a fair randomization. The contestant chooses Door 1. Monty
Hall, for reasons best known to himself, opens Door 3 revealing a goat.
We know that whatever probability mechanism is used by Monty for this
purpose, the conditional probability that switching will give the car
is at least 1/2. We know that the unconditional probability (ie not
conditioning on the door chosen by the contestant, nor the door opened
by Monty) is 2/3.
Always switching gives the car with unconditional probability 2/3, always staying gives it with probability 1/3. Nobody in their right mind could imagine that there could exist some mixed strategy (sometimes staying, sometimes switching, perhaps with the help of some randomization device, and all depending on which doors were chosen and opened) which would give you a better overall (ie unconditional) chance than 2/3 of getting the car.
This is true, of course. In fact, from the law of total probability, proving the optimality of (unconditional) 2/3 by always switching is equivalent to proving that all the six conditional probabilities of winning by switching, given door chosen and door opened, are at least 1/2. We can prove the latter using Bayes' theorem, or, better I think, using Bayes' rule in a smart way. However both these proofs require some sophistication.
Is there an elementary proof? A short proof using words and ideas, no computations.
Yes there is, and I learnt it from Sasha Gnedin.
However you play there's always a door such that if the car is there, you'll miss it. Consider first deterministic strategies. We only need consider two cases: for "always switching" it's the door you initially chose, and for "sometimes switching" it's a door you won't switch to if you get the option. (If you never switch there are two such doors: just choose one). Ordinary readers won't be interested in randomized strategies but anyone who wants to include these will understand how to do it (now the door where you'ld certainly miss a car has to be a random door, determined by the same coin tosses used to implement the random choices in your own strategy).
Note that the door which has been indicated in this way does not depend on where the car is actually hidden or how the host plays: it just depends on how the player plays. Therefore if the car is initially equally likely to be behind any of the three doors, we run a 1/3 chance that the car will be missed because it's behind this door. Therefore the 2/3 success-chance of always switching can't be beaten.
I would call this a proof by coupling.
The mathematical heart of all exchange paradoxes is encapsulated in a little theorem which I call my "unified solution". It seems to be new.
Statistical ethics of the probiotica trial.
This randomized triple-blind clinical trial of probiotics treatment
for patients with predicted severe acute pancreatitis ended in controversy,
when it transpired at the conclusion of the trial in
December 2007, that rather more patients had died on the treatment
arm of the trial than on the control arm.
It seemed strange that the trial had not been terminated at the interim analysis. The researchers were using a a stopping rule of S.M. Snapinn, by which the trial would to be terminated early either if it were almost certain that the final result would be a significant positive effect of probiotica, or if it were almost certain that the final result would be insignificant. Here is a paper by myself, to appear in Statistica Neerlandica, and, in Dutch, a short article by probabilist Ronald Meester and microbiologist Pieter ter Steeg which appeared in the newspaper Trouw and an open letter to Meester and ter Steeg by biostatisticians Hans van Houwelingen and Theo Stijnen. Also in Dutch there are a series of interviews (early 2008) on the current affairs chat show 'Pauw and Witteman': chairman of the hospital board Geert Blijham, 23 January; patient Jochim Vromans, 24 Jaunary; probiotics expert Eric Claassen, 25 January; leader of the research team Hein Gooszen, 14 February.
Later we obtained the data at the time of the interim analysis. It was given to journalists at a press conference on Feb. 13 2008, but never released to interested scientists. It turned out that the probiotica trial was not terminated for futility (following the Snapinn stopping rule) at the half way interim analysis, through a mis-reading of output of the SPSS package, which, without consulting the user, always reports the smaller p-value of the two one-sided Fisher's exact tests for equality of two binomial probabilities. Proper application of their own stopping rule would have led to early termination of the trial, since according to the criteria set in advance, there was no chance any more that it would result in a positive result for the probiotica treatment. The trial was de facto continued because there was a good chance that it would finally result in a negative result for probiotica. Here are slides of my talk careless statistics costs lives on the subject.
Mathematical Centre (Amsterdam) publications are now available on internet.
Here are two early works which had quite some impact, including
the reprint of my 1979 PhD thesis:
R.D. Gill (1980), Censoring and Stochastic Integrals, MC Tract 124.
R.D. Gill (1983), The sieve method as an alternative to dollar-unit sampling: the mathematical background, Report SN 12
Another useful link is to my Saint Flour lectures on survival analysis.
Product-integrals are to
products, as integrals are to sums. Though they have been around for
more than a hundred years, they never became part of the standard
toolbox, possibly because no-one invented the right mathematical symbol
for them. I made a try quite some years ago, though they still have not
caught on yet. With the crucial help of JC Loredo, my efforts resulted
prodint.zip, files for getting beautiful
\prodi and \Prodi and \PRODI symbols in your LaTeX, and Loredo.ttf,
a TrueType font for ordinary word processing. It is not that difficult
these days to get new fonts into your latex, see for instance TUG's
font installation instructions.