Damned lies and statistics

A closer look at statistics in the news

OK Cupid, an online dating site, has caused a bit of a stir recently about performing experiments on their users. But even without the ethical questions there’s reason to be skeptical about what their data can actually tell us.

Big Data, the book by Viktor Mayer-Schonberger and Kenneth Cukier, talks about two phenomena they believe will drive a big data revolution: ‘Digital exhaust’ and ‘N equals all’. The first refers to the trail of information we leave behind when using the internet that are the residue of clicks and typing. Read more

In news that will delight statisticians everywhere the distinction between the mean and the median finally has the political profile it deserves.

Yesterday Sir Andrew Dilnot, chair of the UK statistical authority, wrote a letter clarifying an ongoing debate between Labour and Conservative politicians on waiting times in accident and emergency rooms. Read more

Racial prejudice is growing in Britain, at least according to the headline on the front of the Guardian newspaper this morning. The paper describes a “Rising tide of race prejudice across Britain” based on new data from the British Social Attitudes Survey.

The BSA asked respondents whether they’d describe themselves as prejudiced against people of other races. The Guardian aggregated those who said they were very prejudiced and those who said they had a little prejudice.

It is true that this proportion has risen recently, from 27 per cent in 2012 to 32 per cent in 2013, but the long term trend is decline.

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Kate Allen

Last month, in advance of a report on 14 hospital trusts with relatively high death rates, it was widely reported that there had been 13,000 “unnecessary” deaths.

But, as a leading academic points out in today’s British Medical Journal, this demonstrates an epic lack of understanding of the concept of an average.

The 13,000 figure is the difference between the actual number of deaths in the 14 hospitals compared to the “expected” level. But what some writers failed to understand is that the “expected” level equated to the national average. As a result much of the coverage was seriously misleading, according to David Spiegelhalter, Winton professor for the public understanding of risk at the University of Cambridge. Read more

Data visualisation is the latest fashion in numerate journalism, albeit one that harks back to the likes of Florence Nightingale. Data visualisation creates powerful, elegant images from complex data. It’s like good prose: a pleasure to experience and a force for good in the right hands, but also seductive and potentially deceptive. Because we have less experience of data visualisation than of rhetoric, we are naive, and allow ourselves to be dazzled. Too much data visualisation is the statistical equivalent of dazzle camouflage: striking looks grab our attention but either fail to convey useful information or actively misdirect us.

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Chris Cook

Next week, the Department for Education is unveiling access to the Key Stage 4 league tables. The interesting policy thing to watch for is how many schools are under the floor target – these schools are at risk of a takeover by an academy chain. This is not straightforward: academy chains are not all equal, there is a limit to how far they can grow -and some of them are already struggling with the load they have.

Based on early drafts of the data returns (and assuming the DfE doesn’t calculate this stuff in an odd way*), about 240 schools last year failed to get 40 per cent of their pupils Cs in English, maths and three others. Of these, about 220 had a below-average number of pupils making “adequate progress” in English and maths, putting them at risk of takeovers.

Before the DfE starts its getting-tough-on-failing-schools routine, I thought I would update and republish two graphs. First, I have worked out what happens if you remove the failing schools. Answer: not an enormous amount. As ever, these are average results for poor pupils (on the left) running over to the richest (on the right).

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