Welcome to Understanding Uncertainty

Welcome to the site that tries to make sense of chance, risk, luck, uncertainty and probability. Mathematics won't tell us what to do, but we think that understanding the numbers can help us deal with our own uncertainty and allow us to look critically at stories in the media.


Sex by Numbers, by David Spiegelhalter, is now available for purchase!

Details of reviews, interviews, (and errors) are all featured here.

Do you have a coincidence story? David Spiegelhalter is collecting them over at http://cambridgecoincidences.org.

Elsewhere on UnderstandingUncertainty:

Women listen and men look? How to best communicate risk to support decision making

Verena Rieser

When my family plans a trip to the beach in Scotland, there is always a high chance of rain. So I always pack everything: from sunscreen to waterproofs. But would I have reached the same conclusion listening to the weather forecast on the radio or when checking the weather app on my phone? And would my husband have done the same?

Exploring the language of chance in a sensitive context

What words are appropriate when describing the unavoidable unpredictability of real life – what we might casually call ‘chance’?

The risks of Big Data – or why I am not worried about brain tumours.

In a careful study published last week, Socioeconomic position and the risk of brain tumour: a Swedish national population-based cohort study, the authors examined the association between the socio-economic status of men and women in Sweden with diagnosis of brain tumours over 18 years. One of the main findings is shown below.

The risks of trying to be funny

I’ve had a lot of publicity over the last few days, but none of it was welcome. It arose from the story below from the Daily Telegraph of June 6 with the headline “Britons are having less sex, and Game of Thrones could be to blame, says Cambridge professor


The importance of what you don’t see

Remember all those autism stories over the last few weeks? You don’t? There’s a reason for that.

Medicine, poison, poison, poison, ……

Yesterday the Chief Medical Officer announced new guidelines for alcohol consumption. The Summary says,

The proposed guidelines and the expert group report that underpins them, have been developed on the basis of the following principles:

Jeremy Hunt, the Guardian, and the importance of getting the stats right

On Thursday November 19th the printed version of the Guardian had the headline “Experts dispute Hunt's claim on weekend hospital treatment“ [online version here]. But it was not only Health Secretary Jeremy Hunt who gave a misleading statement – the Guardian also made a serious error about statistics.

HRT, breast cancer, and the framing of risks

The way that risks are 'framed' can make a big impression on their apparent magnitude. The controversy following the recent report by NICE on hormone replacement therapy (HRT) provides a fine example.

Is it fair that a single bad outcome should label a surgeon as an outlier?

Surgeons are increasingly subject to statistical monitoring, and named results may be made publicly available. But consider a surgeon in a low-risk specialty who has had a successful and blameless career, until a combination of circumstances, possibly beyond their control, contribute to a single patient dying. They then find they are officially labeled as an ‘outlier’ and subject to formal investigation, all because of a purely statistical criterion. Is this fair?


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