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Poisson Distribution
The Poisson can be used to model soccer matches. The graph below
shows the the distribution of goals scored by a team playing at home over
a season in a league competition. Their average was 1.00
goals/match.
As can be seen, the Poisson model describes the team's goal scoring
achievements over the season. However, this model should be treated
with care as there are a number of caveats, including:
Competing teams should be of comparable ability
Statistics should be compiled from games where the opposing teams are
of comparable ability, this may be reasonable for games played in a
league competition, however, games played in knock-out competitions may
give a distorted impression of the team's ability. A good example
is the early rounds of the FA Cup where well funded Premier League
teams can be drawn against ones from lower leagues. Scores of
greater than 4 goals are unusual.
Home and away performance may different
Typically teams perform better on their home ground that at away
fixtures, therefore care should be taken to separate the two.
Teams change over the season
For the model to have any validity, the composition of the team should
be constant over the season with the same manager working with the same
squad. However, in reality this is seldom the case. Players
come and go because of loans and transfers. Within the squad
availability will be determined by injuries and suspensions. It may
be able to get a better model of a team's performance by considering the
player's who are available for a given game rather than rely on historic
performance.
Remove Penalties and Own Goals from the data
Whilst the ability of a team to capitalize on the opportunity created
by a penalty is important, penalties arise from a weakness in the
opposing team and should be treated as one of the chance elements the
game.
Whilst statistics can be an attempt at informed speculation, don't
ignore the roll of chance otherwise football would not have its magic.
Page Updated: 02-Mar-2008
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