david's blog

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.

Visualising uncertainty about the future

A great use of a 'spaghetti plot' of multiple model predictions for Hurricane Katia in this NBC news bulletin .


possible hurricane paths

Spotting a hoax using statistics

A report claiming that users of the Internet Explorer browser had lower IQs than users of other browsers has been revealed to be a hoax. I had been asked to comment on the report by BBC Technology and had got suspicious about the figures. The perpetrators of the hoax, which had received extensive coverage, have listed the reasons why they should have been detected, but did not include 'dubious statistics' in their list.

When does a single vote count?

1,362 Cambridge academics recently voted on ‘no confidence’ in the universities minister David Willetts, and this resulted in an exact draw with 681 voting each way: by the rules it meant the motion, or ‘Grace’, was not passed. A natural question to ask is: what was the chance of this happening?

Another ghastly graphic in the TImes

The Times has got another classic graphic today, which manages to be hideous, misleading and incomprehensible all at the same time - quite a feat. Why is this a pie-chart? Never mind, it all provides fine material for getting laughs when giving talks.

hideous, misleading and incomprehensible all at the same time


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