# understanding uncertainty

 One in nine women will get breast cancer in her lifetime, and it seems sensible to screen women for breast cancer to treat them as early as possible. But, as David Spiegelhalter explains, screening is a controversial issue. On May 22nd 2009 the English Premier league had one more match day ahead, with West Bromwich Albion at the bottom of the league and Manchester United at the top, sure to remain there. Taking up a challenge from a BBC radio programme, David Spiegelhalterand Yin-Lam Ng used their statistical finesse to predict the outcome of the last matches — and they were 90% correct. Find out how they did it. Would you prefer a game with a 90% chance of winning, or one with a 10% chance of losing? You might scratch your head and say it's the same thing, and you'd be right, but research has shown that people's perception of risk is surprisingly vulnerable to the way it's presented. In this article David Spiegelhalter and Mike Pearson explore how risk can be spun and there's an interactive animation for you to have a go yourself. This may seem like an odd question — after all, he’s won — but it opens up some deep philosophical issues surrounding probability. David Spiegelhalter investigates how probability can be defined. Well, no-one knows exactly, but using stats you can make a good guess. This article tells you how and has an interactive life expectancy calculator. Do you dare to find out? You meet an old friend on holiday, you find your colleague shares your birthday, you win the lottery. Exactly how rare are these rare events? David Spiegelhalter investigates in his regular column on uncertainty and risk. This is the second part of our new column on risk and uncertainty. David Spiegelhalter, Winton Professor for the Public Understanding of Risk at the University of Cambridge, continues examining league tables using the Premier League as an example. Find out just how much — or how little — these simple rankings can tell you. League tables are controversial and for good reason. Few things are simple enough to be measured by a single outcome like, for example, the number of exam passes or successful heart operations. But even if we do accept a single yardstick, we haven't yet reckoned with chance, which by itself can produce apparent patterns to delight any tabloid editor. What's the risk of passive smoking? Or climate change? How big is the terrorist threat? And should we trust league tables? These issues concern all of us, but it's not always easy to make sense of the barrage of media information. David Spiegelhalter, Winton Professor for the Public Understanding of Risk, gives Plus his take on uncertainty.