Go figure: Research for piece on how journalists calculate odds - can you help?

RECENTLY it was reported that the arrival of identical triplets was an event which had a 200 million to one chance.

Several people contacted me through my blog about multiple births to complain that this couldn't be the case. (The last time identical triplets were reported, just a few months ago, they came in at 150,000 to one.)

So I pitched it and now I'm working on a piece.

Applying such statistics in stories isn’t limited to detailing unusual births – there’s also all the health stories, among others, – where children or adults are reported to have a “one in a million” chance of surviving or contracting a certain condition, or something...

So, I'm reporting on:

* Where do journalists get these figures from?
* Are they accurate?
* Why are they deemed necessary?
* Do readers/listeners/viewers believe them?
* Are they ever challenged?
* What effect, if any, does their use have on consumers’ impression of the media?

If this is something you have experience of, or a view on, then please get in touch.