Tim: Well, how do we get a grip on the critical figures, the important numbers that surround us? I mean there are some very simple things that anybody can do. So, one thing, which is something More or Less has been campaigning on for years, is just to ask yourself some basic questions. Number one, that number that I just heard that some politician spat out at me, or some journalist recited, is that actually a big number? When someone is quoting a £100 million of spending, you think to yourself, well hang on, there are sixty million people in the country, so £100 million of spending, oh hang on, did they just reveal that that was over three years? Okay, so that’s about £30 million a year for sixty million people so that’s roughly 50p per person per year. And that’s not very complicated maths. Now we understand whether to judge this as a large number or not.

I mean the second thing that you can do, if your intuition doesn’t back that up, is we mostly have access to the internet now. It’s very, very quick and easy just to check something, whether something makes sense. I was recently having an argument with an organisation. They pointed out that the Green Belt has been shrinking by three square miles a year; that’s three square miles a year has been given over to development. And so that sounds very worrying. So, is that a big number principle? So if they said well hang on a moment, is three square miles a year a lot? And I have no idea, off the top of my head, I don’t really know how big three square miles is. I don’t know how big the Green Belt is. But you can very quickly check, and if I recall correctly, the Green Belt around London is about 2,000 square miles. So three square miles a year is not nothing, but it would take 66 years for 10% of it to disappear. And that was available to anybody with an internet connection, which may of us have in offices, many of us have at home, you can very quickly compare.

And then a third thing you always want to ask, which is I think is a related question, is just to say well, that number that I’ve heard, what is that compared to? If someone says that fifty people die in some particular way, or because of some particular disease, just ask yourself, well hang on a minute, if this disease wasn’t present, how many people would be dying? If this condition wasn’t present, if this policy had been changed, what would be going on? There was a very interesting example of that in the last series of More or Less about rail accidents, and we look at the number of people who die in accidents on the railways and it looks very worrying, but when you actually compare it to the number of people who used to die in rail accidents, the rate has been falling fairly dramatically. So obviously every death is a death too many, but just that question, well what are we actually comparing this to, I think is very important. And, to be honest, we all have the mental arithmetic skills, the research skills to ask ourselves these very simple questions.

So we shouldn’t take statistics at face value then?

Tim: Context is very important. I’m not saying the statistic is wrong. I’m not saying when you see the statistic on the number of people who die on the railways, or the rate at which Green Belt land is being given over to development, I’m not saying that these statistics are made up. I’m just saying that unless you make some relevant comparisons, to ask yourself well how much is this per person, or how much is this compared to that, then you don’t really know whether what you’re seeing is important or worrying or good news or bad news, you don’t really have any way of interpreting it at all.

you mustn’t throw your political sensibilities out of the window when faced with numbers

Kevin: It’s really that people sometimes think of statistics as being some absolute truth that’s sitting there, but you mustn’t throw your, what you might call, political sensibilities out of the window when faced with numbers. We’re not saying the numbers are wrong. We’re not saying people are using the numbers to lie. What we’re saying is there may be other things you need to look at, and asking the sort of questions that can help you to see if there is something else you might have looked at instead that might be more relevant, might be differently relevant, might put a different angle on it so that you can actually see a fuller picture.

Tim: Most of the categories that we use for statistical analysis are entirely artificial, they’re constructed for a purpose, and if the statisticians are good, then they’ll be constructed in a useful and informative way, and if the statisticians are bad, then the categories won’t make much sense. But good or bad, we have to understand what the categories mean. We know what three means, and we know what a square mile is. Well we know what the definition of a square mile is, not all of us have an image in our minds about how big a square mile really is, how many football pitches it is, for example. But categories like the Green Belt, well that’s a particular definition, it’s a political definition, and it may not actually accord with our common sense intuition. And the same thing applies to the concept of being given over to development. What does it mean to be given over to development? Does that mean any kind of development? Does that mean that houses are actually being built on this land or just that houses may in the future be built on this land? This is just an example.

So if we want to understand what’s really going on, we have to ask them some reasonably sensible questions about how these categories are constructed. That’s something I think that More or Less tries to do, and that of course is something you can’t always do with common sense. I mean common sense alone doesn’t tell you what the Green Belt is, common sense alone doesn’t tell you want given over to development means, but More or Less looks at this sort of question and sometimes finds surprising answers.

What do you think makes More or Less work?

Kevin: I think More or Less works because it tells good stories. A kind of strange thing to say about numbers but that’s what More or Less does. It tells fascinating stories, it tells interesting stories, they’re stories about numbers, but they’re stories that are told in ways that build on people’s experience, that will be comprehensible to people who haven’t got huge technical training in economics or statistics, or whatever it is, and they’re interesting stories. There’s a variety of stories in any programme. Almost all More or Less programmes have three, four, five different stories that they tell in the course of the programme. And the standard of the story telling is really good, and that’s an important reason why it works. It tells a story so we can understand, that are clearly relevant to us, and they’re interesting.

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Content last updated: 22/10/2007

About our expert

Kevin McConway is a Senior Lecturer in the Department of Mathematics and Statistics at the Open University, where he teaches statistics and health studies, and researches in several areas including statistical theory, health service organization, ecology and evolution.

He has degrees in mathematics, statistics, psychology and business from the Universities of Cambridge and London and the Open University. Kevin originally comes from rural Northumberland but is now a long-term Milton Keynes resident.