Wednesday, 21 May 2014

History hour

This is kind of cool $-$ that's an article by Joseph Mazur, appeared in The Guardian with a very brief (but interesting) discussion of the origin of mathematical symbols. I had never really thought about it and basically gave the use of familiar symbols for granted. 

But, apparently, the first recorded instance of the use of the equality symbol $=$ is in Robert Recorde's book on algebra (The Whetstone of Witte), in which he says:
"Howbeit, for easy alteration of equations, I will propound a few examples, because the extraction of their roots, may the more aptly be wrought. And to avoid the tedious repetition of these words: is equal to: I will set as I do often in work use, a pair of parallels, or Gemini lines of one length, thus =====, because no 2 things, can be more equal." 
(incidentally, the equation he referred to was $14x + 15 = 71$).

Tuesday, 13 May 2014

RSS Young Statisticians Writing Competition

Significance and the Young Statisticians Section of the Royal Statistical Society host an annual competition to promote and encourage top-class writing about statistics. This year’s competition closes on 30 May 2014.

Here is link to an article on the Significance website, which explains the competition and the entry criteria.

This year, three finalists will be invited to present their work at a special session of the RSS Conference in Sheffield, in September, where the overall winner will be announced. As usual, the winning article will be published in Significance. 

Saturday, 10 May 2014


I like the way Channel 4 news prioritise their stories (that's their homepage as of 12.06PM $-$ below the one about Mrs President Obama, but above the one about Mr President Putin...

Thursday, 8 May 2014

UCL Biostats Network Symposium 3

We've finalised the line up for the next UCL Biostatistics Network Symposium on "Contemporary Statistical Methods in Medical Research".

This year we'll have two sessions:
1. Risk prediction models  in Health research 
$-$ Ian White, MRC Biostatistics Unit, Cambridge 
$-$ Ewout Steyerberg, University Medical Center, Rotterdam
$-$ Menelaos Pavlou, UCL Statistical Science

2. What you cannot do with observational data
$-$ Irene Petersen, UCL Primary Care and Population Health 
$-$ Frank Windmeijer, Centre for Market and Public Organisation, University of Bristol
$-$ Aidan O'Keeffe, UCL Statistical Science

Not without some controversy (you might have seen this if you follow the allstat mailing list), the symposium (by the way, I think the PhDComics cartoon on how you should call an academic event is awesome!) is free for UCL members.

Non UCL members will have to pay a (I think very reasonable) fee of £25 $-$ details here.

Friday, 2 May 2014

In the media

Yesterday, UCL News Office issued this press release which mentions our (that's Marta and me) paper on the Eurovision contest, which has just been published in the Journal of Applied Statistics.

The idea of the paper was to try and quantify the presence of "bias" in the votes, as is sometimes (in fact quite often) suggested in the media. 

In the model, we have "controlled" for some contextual and act-specific related factors (such as the sex of the performer and the language of the song), but really what we wanted to model was the "residual", structured effect, which could explain (at least partially) why two performers sharing common features get different scores from different voters.

Basically we modelled a structured effect $\alpha_{vp}$ for each combination of voters ($v$) and performers ($p$) over the repeated measurements in the last 20 years or so. This is defined as a function of three main factors:

  1. A "geographical" effect $\psi$, which accounts for potential bias due to spatial proximity;
  2. A "cultural" effect $\delta_{{R_v}p}$, which we use to describe the underlying "clustering" of voters in a set of groups $-$ we term this "cultural" in a rather broad sense. The clustering estimation is embedded in the model;
  3. A "migration" effect $\phi$, which accounts for the fact that voters where a large population originally from the performer's country may inflate the voting pattern in their favour.
As it happens, our model doesn't seem to uncover any evidence of negative bias $-$ no systematic low scores for any given performer $-$ although there is some (rather weak) evidence of positive bias, eg some countries showing higher propensity to score some performers higher than others.

By "standardising" the effects 
$\alpha_{vp}$ (centering them around their mean and re-scaling in terms of their standard deviation), we can compare them. This is the graph of propensity to vote for the UK.
We arbitrarily (but reasonably, as the $\alpha_{vp}$ are pretty much Normally distributed in their posteriors) set the threshold for "substantial" bias at $\pm$ 1.96. As you can see, while a couple of voters (Ireland, Malta and Italy) show on average a positive attitude towards the UK acts, nothing is really going on $-$ basically all credible intervals intersect 0. Most importantly, none is above or below the "bias thresholds".

We're starting to get some coverage (in some cases from the most unexpected sources!) $-$ some examples are here, here. I've also been called on the phone by The Sun (I was quite nervous about it $-$ hopefully I haven't embarrassed myself...)

On demand (but on a very serious topic)

My friend Virgilio has posted this on his Facebook page and invited me to comment. It is an article by a Spanish cardiologist that tells the story of a patient who has suffered a second stroke in a short amount of time $-$ as it turns out, the medication he was supposed to be taking was far too expensive for him, so he stopped the treatment, which presumably led to his second stroke.

Of course the individual story of a single, unemployed patient who cannot afford treatment is tragic. And of course, as I understand it, the general situation in Spain is not OK at the moment and this is likely to not be an isolated case, alas. 

But I still think that the whole rationale of optimizing health resources allocation so that the overall population, on average, benefit from them, makes sense. Of course, how decisions (eg about pricing) are actually made, it's another matter and I'm not too familiar with the details of the Spanish system to comment on that. 

Also, of course as I said that one story is tragic. But reporting bias may be present here: can we discount the possibility that many other cases do benefit from the fact that some form of prioritisation is made? For example, public money is probably saved from not giving treatments for other disease on the public health service, This means that (OK: probably not enough money, but at least some) money can be allocated on this area.