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Understanding Uncertainty wrote a new blog post titled Exploring the language of chance in a sensitive context
What words are appropriate when describing the unavoidable unpredictability of real life – what we might casually call ‘chance’? This became a vital question in a recent project to build a website explaining survival outcomes in children’s heart surgery: this was a fine collaboration between CORU at UCL, Sense about Science, King's College London Psychology, and the Children's Heart Federation. Put rather coldly, the PRAIS (Partial Risk Adjustment in Surgery) risk-adjustment system uses information on each case to assess an individual’s probability of survival, and these probabilities are...
1139 days ago
Understanding Uncertainty wrote a new blog post titled The risks of Big Data – or why I am not worried about brain tumours.
In a careful study published last week, Socioeconomic position and the risk of brain tumour: a Swedish national population-based cohort study, the authors examined the association between the socio-economic status of men and women in Sweden with diagnosis of brain tumours over 18 years. One of the main findings is shown below. Part of a table showing a significantly increased incidence of gliomas in men with more education: the final column shows the relative risks adjusted for marital status and income. The press release was moderately over-enthusiastic. It correctly said that no causal...
1178 days ago
Understanding Uncertainty wrote a new blog post titled The risks of trying to be funny
I’ve had a lot of publicity over the last few days, but none of it was welcome. It arose from the story below from the Daily Telegraph of June 6 with the headline “Britons are having less sex, and Game of Thrones could be to blame, says Cambridge professor” I really did say all this. At a talk for the general public at the Hay Festival plugging Sex by Numbers, I was talking about the decline in sexual activity over the last 20 years identified by the NATSAL survey, and said that the press was obsessed with the reasons for this. As a statistician, I couldn’t say why this decline had...
1199 days ago
Understanding Uncertainty wrote a new blog post titled The importance of what you don’t see
Remember all those autism stories over the last few weeks? You don’t? There’s a reason for that. The first story you did not hear about concerned a claimed association between autism and aerial crop-spraying of pyrethroids, arising from a press release from the American Association of Pediatrics of a non-peer-reviewed poster at a conference. The Science Media Centre asked for quotes from their cohort of scientists while the story was still embargoed, and the comments received were so uniformly negative that it received no coverage in the UK. Even in the US there were only limited...
1212 days ago
Understanding Uncertainty wrote a new blog post titled Medicine, poison, poison, poison, ……
Yesterday the Chief Medical Officer announced new guidelines for alcohol consumption. The Summary says, The proposed guidelines and the expert group report that underpins them, have been developed on the basis of the following principles: People have a right to accurate information and clear advice about alcohol and its health risks. There is a responsibility on Government to ensure this information is provided for citizens in an open way, so they can make informed choices. This admirable aim of treating the public as adults capable of making up their own minds seems in stark contrast with...
1340 days ago
Understanding Uncertainty wrote a new blog post titled Jeremy Hunt, the Guardian, and the importance of getting the stats right
On Thursday November 19th the printed version of the Guardian had the headline “Experts dispute Hunt's claim on weekend hospital treatment“ [online version here]. But it was not only Health Secretary Jeremy Hunt who gave a misleading statement – the Guardian also made a serious error about statistics. The background to the story is Hunt’s comment in the Commons on October 28th, that “currently, across all key specialties, in only 10% of our hospitals are patients seen by a consultant within 14 hours of being admitted at the weekend”. This simple statement managed to achieve two errors and...
1399 days ago
Understanding Uncertainty wrote a new blog post titled HRT, breast cancer, and the framing of risks
The way that risks are 'framed' can make a big impression on their apparent magnitude. The controversy following the recent report by NICE on hormone replacement therapy (HRT) provides a fine example. HRT is known to increase the risk of some cancers, and the Daily Mail reported claims that these risks were not given sufficient attention by NICE. In particular, the journalist quotes Professor Val Beral as saying ‘About one million UK women are currently using hormones for the menopause, and among them about 10,000 extra breast cancers are estimated to occur in the next ten years … [and]...
1406 days ago
Understanding Uncertainty wrote a new blog post titled Is it fair that a single bad outcome should label a surgeon as an outlier?
Surgeons are increasingly subject to statistical monitoring, and named results may be made publicly available. But consider a surgeon in a low-risk specialty who has had a successful and blameless career, until a combination of circumstances, possibly beyond their control, contribute to a single patient dying. They then find they are officially labeled as an ‘outlier’ and subject to formal investigation, all because of a purely statistical criterion. Is this fair? The 'outlier' procedure works as follows. Adverse outcomes (such as deaths) are accumulated over a fixed period, say 1 or 3...
1432 days ago
Understanding Uncertainty wrote a new blog post titled Why live interviews are a particular challenge for statisticians.
I like doing live interviews for radio or TV – it’s exciting and they can’t edit what you say. The programme is almost inevitably running late, so last Saturday morning when I did an interview for Radio 4’s Today I remembered my media training and had prepared carefully to get my points over before they cut me off. But it was a nightmare. Well maybe that’s an exaggeration, but the start went very badly. The topic was pre-election polls, and the researcher had assured me that they would ask me about the stuff in my recent blog about what went wrong and what might be done in future. So...
1586 days ago
Understanding Uncertainty wrote a new blog post titled Was anyone right about the pre-election polls?
There has been much wailing and gnashing of blogs since the dismal performance of the pre-election polls last week. These had confidently and consistently predicted a rough tie in vote-share between Labour and Conservative, but when the votes were counted the Conservatives had a 6.5% lead. Comparison of vote-share BBC Poll of polls on May 6th, and actual results on May 7th. Party Polls vote share Actual vote share Conservatives 34% 36.9% Labour 33% 30.4% UKIP 13% 12.6% Liberal Democrats 8% 7.9% The pre-election estimates of vote-share led May 2015 to predict that Ed...
1590 days ago
Understanding Uncertainty wrote a new blog post titled Sensationalist promotion by the World Cancer Research Fund
Today the Daily Telegraph featured the powerful headline "Just three alcoholic drinks a day can cause liver cancer, warns new study" , based on a press release from the World Cancer Research Fund headed “Three alcoholic drinks a day can cause liver cancer, new research finds”. But examining the WCRF report in detail reveals a somewhat more nuanced story. In particular the report says “No conclusion was possible for intakes below 45 grams per day.” (page 27) – a standard UK unit is 8gms, so this is nearly 6 units a day, double the male and triple the female recommended limits. It is 500 mls...
1625 days ago
Understanding Uncertainty wrote a new blog post titled Misleading conclusions from alcohol protection study
The Daily Mail today declared that "Drinking is only good for you if you are a woman over 65", while the Times trumpeted that "Alcohol has no health benefits after all". But these headlines are without serious foundation, and through no fault of the journalists. They are based on a paper in this week's British Medical Journal which uses data from the Health Survey of England to investigate the protective effect of low consumption of alcohol. Other studies that have suggested a protective effect have compared drinkers with non-drinkers, but the authors say the latter group will include former...
1682 days ago
Understanding Uncertainty wrote a new blog post titled How many hours of life did Obama lose in Delhi?
President Barack Obama recently spent 3 days in Delhi, and it’s claimed that during this period the air pollution knocked 6 hours off his life. So who was responsible for this number? Well, …. me. I gave this estimate to a Bloomberg journalist based in New Delhi who had got hold of me through some previous coverage of our concept of ‘microlives’ applied to air pollution. So where did I get the ‘6 hours’ figure from? We need to go through a number of stages. An authoritative study in the New England Journal of Medicine examined changes over 40 years of fine-particulate data in 211 counties...
1692 days ago
Understanding Uncertainty wrote a new blog post titled Luck and Cancer
I was on Radio PM and BBC News Channel yesterday discussing the study published in Science " Variation in cancer risk among tissues can be explained by the number of stem cell divisions ". This had been reported by much of the press as showing that “the majority of cancer cases are down to sheer bad luck”. But the study made no such claim, and so how did these headlines come about? The main findings are shown in the summary figure from Science's News section, reproduced in a slightly edited form below. Figure from Science: blue dots added by me. The headline underneath is Science's...
1721 days ago
Understanding Uncertainty wrote a new blog post titled Sub-editing in the Times
A story in monday's Times had the following dramatic headline: I started the article with interest, wondering what flaws in the breast screening programme had been exposed. But the article turned out to be a good description by Chris Smyth of a study of how Ashkenazi women, who are at high risk of carrying the BRCA gene, which in turn increases the risk of breast and ovarian cancer, were not being adequately screened for the gene. Systematically testing all this sub-population would be cost-effective. All very good, but little to do with the failure in breast cancer screening apparently...
1752 days ago
Understanding Uncertainty wrote a new blog post titled Is prostitution really worth £5.7 billion a year?
The EU has demanded rapid payment of £1.7 billion from the UK because our economy has done better than predicted, and some of this is due to the prostitution market now being considered as part of our National Accounts and contributing an extra £5.3 billion to GDP at 2009 prices, which is 0.35% of GDP, half that of agriculture. But is this a reasonable estimate? This £5.3 billion figure was assessed by the Office of National Statistics in May 2014 based on the following assumptions, derived from this analysis. To quote the ONS: Number of prostitutes in UK: 61,000 Average cost per visit:...
1791 days ago
Understanding Uncertainty wrote a new blog post titled What's the most likely age to die?
It’s all very well telling someone their life expectancy but this does not communicate the variability around that central value. But the life tables published by the Office for National Statistics (ONS) have a convenient column labeled $d_x$ - this is the probability density for survival, expressed as the expected number of deaths at each age out of 10,000 births, assuming the current mortality rates continue. The curves for women and men are shown below, using the life tables for 2010-2012. The distributions have a small peak for babies dying in the first year of life, and then a long...
1823 days ago
Understanding Uncertainty wrote a new blog post titled Using expected frequencies when teaching probability
The July 2014 Mathematics Programmes of Study: Key Stage 4 (GCSE) specifies under Probability {calculate and interpret conditional probabilities through representation using expected frequencies with two-way tables, tree diagrams and Venn diagrams}. - the brackets and bold case means this comes under additional mathematical content to be taught to more highly attaining pupils. The use of the term ‘expected frequencies’ is novel and not widely known in mathematics education. The basic idea is very simple: instead of saying “the probability of X is 0.20 (or 20%)”, we would say “out of 100...
1833 days ago
Understanding Uncertainty wrote a new blog post titled Another tragic cluster - but how surprised should we be?
Sadly another passenger plane crashed yesterday - the third in 8 days, the Air Algerie flight on July 24th, the TransAsia flight in Taiwan on July 23rd, and Malaysian Airlines in Ukraine on July 17th. Does this mean that flying is becoming more dangerous and we should keep off planes? The following analysis may appear cold-hearted, but is not intended to diminish the impact of this tragic loss on the people and families involved. The Plane Crash Info website contains the summaries of these three accidents - this site makes powerful reading and is not for those with a fear of flying. Their...
1883 days ago
Understanding Uncertainty wrote a new blog post titled Using metrics to assess research quality
The Higher Education Funding Council for England (HEFCE) is carrying out an independent review of the role of metrics in research assessment, and are encouraging views. I have submitted a (very personal) response, using HEFCE's suggested headings, which is given below in a minimally-edited version. ++++++++++++++++++++++++++++++ You will be getting a lot of detailed reasoned arguments about this topic, so I thought I would provide a more personal perspective from someone whose has done very well out of metrics. Identifying useful metrics for research assessment: I am a statistician, and so...
1914 days ago