I have a confession to make: I am feeling a little nervous. I am making a TV programme for the BBC about chance and uncertainty, and for some reason the producers have told me that I need to do a sky-dive – presumably while they stand safely on solid ground, sipping tea and enjoying the spectacle of me floating gently to earth. Probably. But as I ponder the wisdom of such an undertaking, the statistician in me has been keen to explore the real dangeers of various seemingly high-risk pursuits. There is seemingly no shortage of people apparently willing to scale great heights, or hurl themselves down from them – including me, it seems – turning extreme sports into a multi-billion dollar global industry. Comparing these risks is not a clear-cut task. It is usually fairly straightforward to count the dead bodies. But do we consider these as a proportion of everyone who takes part, or those that attempt more dangerous forms, or per day of activity? And even then it is often difficult to get solid data on how many people are getting up to whatever pursuit turns them on.

It appears to be one of the worst rail disasters in the country in recent years

Two trains have collided in southern Poland, leaving 14 people dead and 50 hurt, local officials say.

The accident occurred on Saturday evening on the Warsaw-Krakow mainline at the small town of Szczekociny, according to Polish TV.
Two express trains, one of which was on the wrong track, collided head-on, a senior railway official said.
Prime Minister Donald Tusk called the accident Poland's "most tragic train catastrophe... in many years."
Mr Tusk arrived at the scene early on Sunday morning, with three other cabinet ministers.
The two trains, comprising 10 carriages in total, were carrying an estimated 350 passengers at the time of the crash.
Helicopter ambulances from Warsaw and Wroclaw helped to take the injured to hospitals.
"The rescue is difficult and complicated," firefighter Jaroslaw Wojtasik told Polish television.

"The damage to the wagons is huge. We have contact with victims. We are approaching very cautiously."
Engineering works
The accident occurred at 21:15 (20:15 GMT), when a train travelling north from Przemysl to Warsaw collided with a southbound train from Warsaw to Krakow.
Scheduled engineering works were taking place on one track at Szczekociny station at the time of the accident.
The Krakow train was on the wrong track, Andrzej Pawlowski, a member of the board of the state railway company PKP, told the TV station TVN24.
Three coaches are reported to be especially damaged, and the rescue operation is focusing on finding passengers there.
The three coaches were "completely destroyed - like a concertina", one eyewitness told the Gazeta Wyborcza newspaper.
Another passenger estimated that his train was travelling about 120km/h (75 mph), when it started braking very sharply.