Tuesday, March 18, 2008

Brisebois: Conclusion and Fallacy

It's getting late in the season and those critics who are surprised about where the Canadiens stand are bringing out all their theories of explanation.

When I come across something like the quote below from hockeybuzz, I have to take issue:

Roman Hamrlik, Andrei Markov, and even Patrice Brisebois have done a lot to stabilize this team.

Allow me to explain. Here is a series of logical arguments:

1) Patrice Brisebois was signed in the summer of 2007.
The Canadiens have improved dramatically since the end of last season.
Therefore, the signing of Patrice Brisebois dramatically improved the Canadiens.

2) Veteran defensemen stabilise teams and give them a platform to succeed.
Patrice Brisebois has played close to 1000 NHL games.
Therefore, Patrice Brisebois has given the Canadiens a platform to succeed this

3) Patrice Brisebois was brought in to help the Canadiens young defensemen.
The Canadiens young defensemen have improved.
Therefore, Patrice Brisebois directly helped to create a stronger Canadiens defense

So, Patrice Brisebois has been absolutely integral to the Canadiens improvement this season, right?

If this is so, how come the conclusions leave us feeling a little bit perplexed. The answer is fairly straightforward: we have observed the experiment of Brisebois in 2007-2008 and would feel fairly confident in declaring that there must be another explanation.

Consider there are several ways in which a logical argument can fall down. If you begin a logical argument based on a premise that is untrue or based on assumption, then the conclusion can be false.

In examples 2) and 3), one can see that a couple of the statements are actually assumptions, if not outright falsehoods: Veteran defensemen stabilise teams and give them a platform to succeed and Patrice Brisebois was brought in to help the Canadiens young defensemen.

How can one argue with the original statement, however, from the hockeybuzz blogger or indeed, logical argument 1)?

The two first premises of argument 1) are statements of fact (if you base improvement on winning percentage, that is), yet the conclusion still feels wrong. The error made here is sometimes called Post hoc ergo propter hoclatin for "after this, therefore because of this".

Following? Now consider the Pastafarian "belief system" in which the decline in the number of pirates has led to global warming:

Since the 1800s, the number of pirates on the seas has steadily declined.
Since the 1800s, global temperatures have been rising.
The decline in pirate numbers has led to global warming.

Now, nobody can rule completely rule out the possibility that Brisebois is the one reason the Habs are better (or even one of the reasons) in a multivariate system like the NHL, just like no one can rule out the worldly importance of pirates. However, unlike our esteemed friend at hockeybuzz, I think many of us would all be a little more open to the latter theory after having to watch Patrice "play" 38 times.

Perhaps if he dressed like a pirate on skates...

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