Angela Saini
speaker
229 appearances
5 recordings
1 series
first heard Jan 2012
last heard Jul 2012
Angela Saini’s voice in public audio — every appearance, attributed to the second.
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Appearances
Well, always on the lookout for a good statistical puzzle, we at More or Less have been finding out.
Press reports have made it sound like a measure of certainty that the Higgs boson has been found.
so one sigma would be low certainty and five sigma high.
In a way, that's right, but in another, more exact way, it's totally wrong.
The reason scientists say sigma is because that's the word used by statisticians when measuring how far something lies from the centre of a bell-shaped normal distribution curve.
In nature, lots of things follow a normal distribution.
Take the heights of adult men.
Average height in the US is between 5 foot 7 to 6 foot 1.
For someone to stand out as one sigma above normal, they would have to be more than 6 foot 1.
For three sigma, they would have to be around 6 foot 7.
And for five sigma, they would have to be more than 7 feet tall.
So in physics, as in life, if something is particularly unusual, it has a higher sigma value.
For the Higgs result to be 5 sigma, the probability of getting the same experimental data, if nothing more than random chance were operating, would have to be 1 in 3,486,914.
This is the threshold at which physicists say they have a discovery.
But remember, this is not necessarily the same as the probability that they found the Higgs boson, only of seeing that particular set of data.
For scientists to be sure that they saw what they think they saw will take many more years.
That's your lot for this week.
If you'd like to sample some vintage episodes of this programme, head to the website at bbcworldservice.com slash more or less.
And if you have a number you'd like us to investigate,
The programme was presented by me, Angela Saini.
Showing 21–40 of 229 · page 2 of 12
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