Saturday, April 25, 2009

Probability lessons may teach children how to weigh life’s odds and be winners

From The Times

Professor wants ‘risk literacy’ on the curriculum

Pupils in every secondary school should be taught the statistical skills they need to make sensible life decisions, one of Britain’s leading mathematicians says.

A basic grasp of statistics and probability — “risk literacy” – is critical to making choices about health, money and even education, yet it is largely ignored by the national curriculum, according to the UK’s only Professor of the Public Understanding of Risk.

David Spiegelhalter, of the University of Cambridge, told The Times that as the internet transformed access to information, it was becoming more important than ever to teach people how best to interpret data.

Familiarity with statistical thinking and the principles of risk could help people to make sense of claims about health hazards and the merits of new drugs, to invest money more wisely, and to choose their children’s schools.

Professor Spiegelhalter has developed programmes for teaching risk literacy, based on familiar subjects such as the National Lottery and football league tables, which his team is introducing to schools through a “Risk Roadshow”. He believes that something similar should be offered as a matter of course.

“I regard myself as part of a movement we call risk literacy,” Professor Spiegelhalter told The Times. “It should be a basic component of discussion about issues in media, politics and in schools.

“We should essentially be teaching the ability to deconstruct the latest media story about a cancer risk or a wonder drug, so people can work out what it means. Really, that should be part of everyone’s language.”

As an aspect of science, risk was “as important as learning about DNA, maybe even more important,” he said. “The only problem is putting it on the curriculum: that can be the kiss of death. At the moment we can do it as part of maths outreach, maths inspiration, which is a real privilege because we can make it fun. It’s not teaching to an exam. But I actually think it should be in there, partly to make the curriculum more interesting.”

Risk literacy could be taught as part of maths, science, or civics and personal and social education, Professor Spiegelhalter said.

His tools include an animation of National Lottery results. While every number has an equal probability of being drawn every week, some have come up much more often than others, through chance alone.

“Number 38 has come out 50 per cent more often than 13, and 38’s been in the lead since about 2000. But that’s so uninteresting: there had to be a number at the top and one at the bottom, and they just happen to be 38 and 13. It’s a great tool for teaching people about chance.”

Such simple examples can be used to explain more complex statistical principles, such as recognising that apparently improbable occurrences are often in fact predictable in a population as large as Britain’s.

“You can tick off story after story that’s probably interesting to the people it happened to, but not statistically unusual at all. There was a recent story about a family in Gloucestershire with three children all born on January 29. We were contacted by a journalist and asked what are the chances of this happening.

“The chances are about one in 135,000, or seven in a million. But there are a million families with three children in the UK. So it’s almost certain that this family is not unique and when the story went online, someone wrote in and said, ‘I was born on the same day as my two brothers’.”

A big problem with the public’s understanding of risk and statistics was that the human mind seemed to be evolved to see individual stories as more significant than they really were.

“We seem to grossly overinterpret immediate stories that happen to individuals around you, and from an evolutionary point of view that might be enormously valuable,” Professor Spiegelhalter said. “It’s better to run away from a predator, even if you’re mistaken. It’s very difficult to think calmly about uncertainty. That’s why it needs to be taught.”

The unfounded scare over the MMR vaccine, and outlandish claims of success for alternative medicines, were prime examples.“One must think all the time of what is not being reported – the dog that didn’t bark. When we see a hole-in-one video on YouTube we are sensible enough to know that this has been selected out of millions of shots that missed. We need to think the same way every time we hear of someone claiming that some new treatment has cured them.”

People needed tools to assess the morass of information about health and other matters that was now available, and statistics could help, he said. “The ability to find information on the internet is increasing, the availability of information is increasing all the time. At the same time, what’s also increasing are the number of people trying to manipulate opinion using ‘sciency’ arguments. It’s very important people understand how evidence is used, variability and uncertainty and so on.”

It was also important to know what sort of statistics to seek out for your purpose, Professor Spiegelhalter said, citing school league tables as an example. These had two different objectives, to help parents to choose schools and to hold schools to account, and the data that best suited each purpose were different.

“If you want to hold a school to account, it’s quite reasonable to allow for the neighbourhood in which it operates,” he said. “So if it’s in a very deprived neighbourhood, you should be comparing them with other deprived schools and adjusting for deprivation. A school might be doing a very good job if it’s getting 40 per cent GCSEs. That’s accountability.

“But if you’re choosing a school for your child, you don’t have to take account of deprivation. In fact that’s completely irrelevant. You choose a school that will be best for your child.”

Reality check

Professor Spiegelhalter’s four rules of risk, which he says everyone should know

Stuff happens We cannot predict exactly how every precise event will turn out, but we can often predict the overall pattern of events surprisingly well

Compare like with like If you want to show that speed cameras reduce road traffic accident rates, don’t just put them in places that have just had a run of accidents

What am I not being told? This person may well have got better after she took this wonder treatment, but how many other people’s stories are not being featured?

Twice not-very-much is still not very much Increasing a tiny risk may not be so important: almost everything interesting might help and it might also harm. The trick is working out the balance for you

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