RE: OT but v.interesting

["Amar Nagi" <amar@xxxxxxx>]

The World's No.1 Science & Technology News Service
Statistical model tackles World Cup predictions
11:34 31 May 02

NewScientist.com news service

A new statistical model of the World Cup football tournament could
provide
a more accurate set of predictions than either bookmakers and
television
pundits, according to Henry Stott, a mathematician at the University of
Warwick, UK.

Stott has used a modelling technique more commonly applied to financial
risk assessment to predict the outcome of every game in the 2002
competition, as well as the ultimate winners.

The approach combines human intuition, in the form of bookmakers' odds,
statistical analysis and brute force computer simulation. Stott first
developed a similar system to pick the winners of the 1998 World Cup
after
entering an office sweepstake.

"I did a much cruder analysis and did quite well," he says.
"Then I started
to realise that it's quite an interesting synthesis of human and
computer
thinking."

Peter Haigh, a statistician at the University of Sussex, says the
approach
is much more comprehensive than regular punditry. "I strongly believe
in
simulations as a reliable way to generate estimations," he told
New
Scientist. "It's based on the sound idea that, if you want to come up
with
an estimate you have to take into account the path to the final."

Twice the chance

Although many bookmakers' favourites Argentina were still given the
greatest chance of winning the tournament (13.2%), the model provides a
number of surprising results. Brazil (9.3%) were given better odds than
France (8.7%), whereas bookmakers rate France's chances almost twice as
high. England (6.9%) were also given a better chance of triumphing than
many people's hot tip Italy (6.7%).

In the case of Brazil, Stott believes recent poor results have overly
affected people's assessment of the team's chances. He cautions that
his
probabilities and bookmaker's odds are only comparable in relative
terms,
because bookmakers reduce their prices in order to give them a profit.

The biggest surprise came in individual matches. Stott's system gave a
much
higher chance that underdogs would upset strong teams than bookmakers.
For
example, South Africa are given only a 10% chance of defeating Spain by
most bookmakers, while Stott calculated this probability to be 28%.

Game of two halves

Stott's method, developed with BBC 5Live, involves calculating the
strength
of each team based on performances during qualification matches, as well
as
official FIFA rankings and bookmakers' odds. But unlike some other
ranking
systems, Stott also included a measure of each team's unpredictability,
or
"patchiness", based on previous results.

For individual matches, one team's strength and unpredictability was
then
compared to that of their opponents to determine the probability that
each
side would win, lose or draw.

To determine the overall probability that a team would win the whole
tournament, Stott used a computer to run hundreds of thousands of
virtual
matches.

Portugal (7.9%) turned out to be the fourth most likely team to become
world champions, after Argentina, Brazil and France. The team with the
lowest probability of ultimate victory chance is China with a tiny 0.3
%
chance, though this means they are still overpriced at bookmakers at
750-1.

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