Understanding (and visualising) risk

Prof Spiegelhalter gave a very thought provoking and informative talk at the University of Leicester

There is ample evidence that humans are frequently bamboozled by statistics, and interpretation of risk factors is an area in which this is most apparent. As an example, research from a number of countries showing that about a quarter of the population cannot correctly answer the question “Which is the highest risk factor: 1 in 100, 1 in 1000, or 1 in 10?” (Galesic and Garcia-Retamero, 2010).

This was just one insight during a fascinating lecture on Quantifying Uncertainty given by David Spiegelhalter, Winton Professor of the Public Understanding of Risk at the University of Cambridge. Spiegelhalter, a Bayesian statistician, began his talk with two quotes which he said were very useful in setting an appropriate perspective:

probability does not exist” Bruno de Finetti
all models are wrong, but some are useful” George Box

In other words, probability is not an intrinsic property of  the outside world, but something we apply to it. Risks associated with a number of activities can be compared using a standardised unit the micromort, invented by Stanford University statistician Ron Howard and defined as a 1-in-a-million chance of dying.  For example – how far can you travel by different means for a risk of one micromort? Answer: driving = 250 miles, cycling = 20, walking = 17, motorcycling = 6, hang-gliding = 8, scuba-diving = 5 and skiing = 0.5. Comparisons of this sort lay at the heart of David Nutt’s famous assertion that taking ecstasy has the same risk as horse-riding.

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Making the best of “Bad Science” (Review)

Harper Perennial edition (2009)

Harper Perennial edition (2009)

If you have not yet read Ben Goldacre’s book Bad Science, then I thoroughly recommend that you do. As readers of his regular Guardian column or his website will already know, Goldacre has embarked on a campaign to root out example of pseudoscience and shoddy science whereever they may be found.

All the usual villians are present – homeopaths, nutritionists, slack journalists, pharmaceutical companies and AIDS dissenters. Some are mentioned by name, but given their alleged predilection for litigation, and since I do not have the time, the money or the inclination to do battle with them in the courts, I shall not repeat their identities here!

It would be wrong, however, to give the impression that Goldacre is merely on a crusade against high profile exponents of “bad science”. True, the author does sometimes betray a little too much glee as he places a bomb under the throne of a media “health expert” (in a way that I found disturbingly reminiscent of the Physiology lecturer, when I was a first year undergraduate, recalling his boyhood experiments on frogs). Nevertheless, Goldacre is keen to emphasise that his purpose is to “teach good science by examining the bad” (p165 in my copy), adding that “the aim of this book is that you should be future-proofed against new variants of bullshit” (p87). Continue reading