Damned lies and statistics

A closer look at statistics in the news

Chris Cook Floor targets and social mobility

January 18, 2013 9:17 am by 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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Posted in Damned lies and statistics, Economics, Education, Statistics, UK |

Chris Cook The maths of exam marks

January 2, 2013 4:30 pm by Chris Cook

At the moment, the Department for Education is considering changes to the league tables and the exam system. This seems an opportune moment to make a simple point about qualification-awarding and accountability: English school examinations are subject to measurement error in a really big way.

Here is a simple thought experiment to flesh it out. Imagine a class of 100 students. Let us specify that each one has a “true” ability that means that one pupil should get one point, one pupil should get two, one should get three and so on – up to 100 marks. Now, let’s award this class one of 10 grades: 90+ gets you an A, 80+ a B and so on.

Let us assume that the tests are perfect. If that were the case, you would get ten individuals in each grade. Easy enough. But what happens if we start introducing errors into the test? We can do that with a set of exotically named (but very simple) “Monte Carlo” estimates, which I calculated using this simple spreadsheet. Read more

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Posted in Damned lies and statistics, Data, Education, UK |

Chris Cook Getting around the official statistics

December 14, 2012 3:16 pm by Chris Cook

Last week, I went to Wolverhampton where I spoke at a local debate, organised by the university and Pat McFadden, the local MP, about the local authority’s school. I was the warm-up act for Lord Adonis, former schools minister, setting the scene about the city’s education system before his talk on lessons on school improvement.

It was interesting event – and the city is clearly considering its future and the role of education within it. There is – judging by my inbox – serious and deep interest in improving schools in the city. One of the things I sought to do was set out Wolvo’s position in relation to the rest of the country – and what statistics about the city tell us.

Here is my presentation: Read more

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Posted in Damned lies and statistics, Data, Data Points, Education, Freedom of Information Act, On the records, Politics, polling and psephology, UK |

Kate Allen Evidence-based policy-making? Don’t bet on it

October 2, 2012 4:46 pm by Kate Allen

If you’re going to have a bet this party conference season, take on an MP – that’s the obvious conclusion from an Ipsos Mori poll for the Royal Statistical Society, which suggests that our elected representatives are simply asking to be fleeced.

As part of its Parliamentary lobbying work, the RSS set a basic probability question for nearly 100 MPs. ‘If you spin a coin twice, what is the probability of getting two heads?’*

More than half of them got the answer wrong.

all MPs Read more

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Posted in Damned lies and statistics, UK |

Emily Cadman Internet refuseniks dig in

August 24, 2012 3:36 pm by Emily Cadman

One of the more interesting aspects of Friday’s ONS release on the UK internet access patterns is the reasons why households don’t have internet access.

Much of the data release is as you would expect: more households have internet access, and more people are using computers daily, a trend especially noticeable among the young. Read more

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Posted in Damned lies and statistics |
From FT.com: Chris Giles August 8, 2012

Britain’s traditional measure of inflation, the retail price index, is broken and needs fixing. The error goes back decades, has cost taxpayers billions, is still costing the exchequer about £1bn a year and has resulted in the rise in living standards being underestimated. Few errors in statistical compilation are quite this serious.

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Posted in Damned lies and statistics, Economics, UK |
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