29 December 2011

The Law of Probability in South America

Sparky Venezuelan President Hugo Chavez thinks the US is giving cancer
to South American leaders. This seems to be on the basis of his
diagnosis of cancer, and a smattering of cancers that have been
detected in the presidents of Brazil, Argentina and Paraguay. BBC
LINK: http://www.bbc.co.uk/news/world-latin-america-16349845
Mr Chavez is reported to have said that this is "difficult to explain
using the law of probabilities". The lifetime cancer incidence is
almost one in three. There are 12 countries in South America. The
leaders of four, who range in age from their 50s to 60s (when cancers
start to get common) have had various types of cancer. This does not
look like a violation of "the law of probabilities" to me - more like
a chance outlier, and not even a very big outlier at that. He's only
remarking upon it because it has happened - if it hadn't happened,
no-one would be saying anything.

As for the evil Americans, Chavez goes on to say: "Would it be strange
if they had developed the technology to induce cancer and nobody knew
about it?" Er, yes, it probably would, and it would also be strange if
everyone knew about it. And it would be strange if they had developed
the technology and chose to use it this way. What is really strange is
that someone who is supposed to be the head of an important country in
South America should make such silly and uninformed statements without
the slightest embarrassment of his ignorance of science and indeed
those mysterious "laws of probability". What he really wants to do is
employ Bayes' Theorem, and phrase the question like this: "GIVEN the
rate of cancers among South American leaders, what is the probability
that the US have been deploying a secret oncogenic technology against
said leaders?" That probability is not going to be terribly high. What
Hugo needs is more evidence. A LOT more evidence.

I wish Mr Chavez and his fellow leaders speedy and complete recoveries
(enough of this silly talk of "battling" and "beating" cancer - cancer
is a disease, not a divine/demonic test of your moral mettle), but
before coming out with silly paranoid nonsense, I do wish they would
learn a little bit more about cancers and probability.

1 comment:

  1. Hugo's n has just become n-1. President Fernandez de Kirchner of Argentina doesn't have thyroid cancer after all: http://www.bbc.co.uk/news/world-latin-america-16456040

    This is of course excellent news, and I'm sure everyone is delighted. Maybe that's a USA plot too...