david's blog

Why it’s important to be pedantic about sigmas and commas

The BBC reported last week that evidence for the Higgs Boson is “around the two-sigma level of certainty” and provides further explanation:

Particle physics has an accepted definition for a "discovery": a five-sigma level of certainty. The number of standard deviations, or sigmas, is a measure of how unlikely it is that an experimental result is simply down to chance rather than a real effect”

This is nice and clear, but it is also wrong, as we have pointed out before in a previous blog by Kevin McConway.

The next Piccadilly line train is leaving from ....

Kings Cross Station now not only has a platform 9$\frac{3}{4}$, but also a platform 0. And for the numerically challenged, there are repeated announcements that 'customers are advised that Platform 0 is situated next to Platform 1'

kings-cross.JPG

I suppose the Underground platforms will now have to be given complex numbers.

The risk of queuing?

Got a short article in the Times today about the UK Border Agency relaxing its checks over the summer.

I wish I had included the following interesting information provided by the excellent Home Office Immigration Statistics April-June 2011. In 2010 there were around 100,000,000 admissions to the UK , and around 19,000 non-asylum individuals were refused entry. That's around 1 in 5000 admissions, about 35 plane-loads.

So someone should be able to estimate how many people were admitted who would otherwise have been refused entry - it may not be very many.

Another doubtful league table?

David Cameron has prominently commented on the recent performance tables concerning adoption in local authorities, in particular the proportion of children whose adoption placement occurs within 12 months. But are the local authorities really as different as they have been made out to be?

A probability paradox?

I recently tweeted a link to this problem drawn on a blackboard, which got a lot of retweets.

Multiple Choice: If you choose an answer to this question at random, what is the chance you will be correct? A) 25% B) 50% C) 60% D) 25%

This is a fun question whose paradoxical, self-referential nature quickly reveals itself – A) seems to be fine until one realizes the D) option is also 25%.

A Maserati for £1

After Dave and Angela Dawes won £101 million on the Euromillions lottery, Radio 5 Live asked me to comment on the different ways one could win a decent amount of money for £1. I chose £100,000, which will buy you a shiny new Maserati ( a Ferrari would be about double that). The recording of my interview is here, and here are the details of my calculations, which I hope are roughly correct.

Surgeons create Frankenstein numbers?

The BBC News website and Radio 4 news both led this morning on the Royal College of Surgeons' report on emergency surgery. The BBC web site states that
'A report by the college highlights figures that show that about 170,000 patients undergo emergency abdominal operations each year. Of these, 100,000 will develop complications and 25,000 of these patients will die.'

The dangers of 'don't worry'

(appeared in the Times, 26th September 2011) - pdf here

Now that the rogue US satellite has crashed into the Pacific we can all come out from under our beds. The biggest bit of the satellite was about the weight of an adult gorilla, although not as soft, and travelled at 100 mph so it sounds rather ominous, but people only take up one 80,000th of the earth’s surface so it would be more than an unlucky day if anyone had been hit. 40 tons of debris got scattered over mainland USA after the Columbia shuttle disaster and nobody was injured, although NASA afterwards concluded there had been around a 1 in 4 chance of some casualties.

Get under the table?

The remnants of the Upper Atmosphere Research Satellite (UARS) are due to hit the earth later today and NASA have put up some details of their risk assessment. But this doesn't say where their '1 in 3200 chance of anyone being hit' comes from, and so can we get this figure from a back-of-an-envelope calculation?

Lottery league tables

The Daily Mail and other media sources have featured league tables for the 'luckiest parts of the country' based on the proportion of the population that have become millionaires by winning the lottery. Straight Statistics have done a nice demolition job on this absurd story, pointing out that any comparison should be based on the number of tickets sold, not the population.

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