Archive for United Kingdom

we have never been unable to develop a reliable predictive model

Posted in Statistics with tags , , , , , , , , , , , , , , , on November 10, 2019 by xi'an

An alarming entry in The Guardian about the huge proportion of councils in the UK using machine-learning software to allocate benefits, detect child abuse or claim fraud. And relying blindly on the outcome of such software, despite their well-documented lack of reliability, uncertainty assessments, and warnings. Blindly in the sense that the impact of their (implemented) decision was not even reviewed, even though a portion of the councils does not consider renewing the contracts. With the appalling statement of the CEO of one software company reported in the title. Blaming further the lack of accessibility [for their company] of the data used by the councils for the impossibility [for the company] of providing risk factors and identifying bias, in an unbelievable newspeak inversion… As pointed out by David Spiegelhalter in the article, the openness should go the other way, namely that the algorithms behind the suggestions (read decisions) should be available to understand why these decisions were made. (A whole series of Guardian articles relate to this as well, under the heading “Automating poverty”.)


Posted in pictures, Travel, University life with tags , , , , on October 27, 2019 by xi'an

revisiting the balance heuristic

Posted in Statistics with tags , , , , , , , on October 24, 2019 by xi'an

Last August, Felipe Medina-Aguayo (a former student at Warwick) and Richard Everitt (who has now joined Warwick) arXived a paper on multiple importance sampling (for normalising constants) that goes “exploring some improvements and variations of the balance heuristic via a novel extended-space representation of the estimator, leading to straightforward annealing schemes for variance reduction purposes”, with the interesting side remark that Rao-Blackwellisation may prove sub-optimal when there are many terms in the proposal family, in the sense that not every term in the mixture gets sampled. As already noticed by Victor Elvira and co-authors, getting rid of the components that are not used being an improvement without inducing a bias. The paper also notices that the loss due to using sample sizes rather than expected sample sizes is of second order, compared with the variance of the compared estimators. It further relates to a completion or auxiliary perspective that reminds me of the approaches we adopted in the population Monte Carlo papers and in the vanilla Rao-Blackwellisation paper. But it somewhat diverges from this literature when entering a simulated annealing perspective, in that the importance distributions it considers are freely chosen as powers of a generic target. It is quite surprising that, despite the normalising weights being unknown, a simulated annealing approach produces an unbiased estimator of the initial normalising constant. While another surprise therein is that the extended target associated to their balance heuristic does not admit the right density as marginal but preserves the same normalising constant… (This paper will be presented at BayesComp 2020.)

unimaginable scale culling

Posted in Books, pictures, Statistics, Travel with tags , , , , , , , , , , , , , on September 17, 2019 by xi'an

Despite the evidence brought by ABC on the inefficiency of culling in massive proportions the British Isles badger population against bovine tuberculosis, the [sorry excuse for a] United Kingdom government has permitted a massive expansion of badger culling, with up to 64,000 animals likely to be killed this autumn… Since the cows are the primary vectors of the disease, what about starting with these captive animals?!

Nature tidbits

Posted in Books, University life with tags , , , , , , , , , , , on September 7, 2019 by xi'an

Before returning a few older issues of Nature to the coffee room of the maths department, a quick look brought out the few following items of interests, besides the great cover above:

  • France showing the biggest decline in overal output among the top 10 countries in the Nature Index Annual Tables.
  • A tribune again the EU’s Plan S, towards funding (private) publishers directly from public (research) money. Why continuing to support commercial journals one way or another?!
  • A short debate on geo-engineering towards climate control, with the dire warning that “little is known about the consequences” [which could be further damaging the chances of human survival on this planet].
  • Another call for the accountability of companies designing AI towards fairness and unbiasedness [provided all agree on the meaning of these terms]
  • A study that argues that the obesity epidemics is more prevalent in rural than urban areas due to a higher recourse to junk food in the former.
  • A data mining venture in India to mine [not read] 73 million computerised journal articles, which is not yet clearly legal as the publishers object to it. Although the EU (and the UK) have laws authorising mining for non-commercial goals. (And India has looser regulations wrt copyright.)

the unsinkable…

Posted in Running with tags , , , , , on July 24, 2019 by xi'an

we need to talk about statistics

Posted in pictures, Statistics, University life with tags , , , , on July 17, 2019 by xi'an