Confirmation Bias

Dave · April 13, 2010 at 11:57 am · Filed Under Mariners 

One of the goals of this blog is to be a rational voice in a sea of emotional response. So, take this post in that vein.

A frequent comment that has been brought up as the M’s struggle to score runs and win games to begin the season has been that it’s okay to freak out about the offense because it was a weakness going into the season, and the first eight games are just evidence of the suspected flaws of the team. I understand why this makes sense on some level, but in reality, it’s just bad analysis in a different package.

That belief is really just a manifestation of confirmation bias, or the natural tendency to weigh evidence that agrees with your preconceived opinion too heavily. Everyone gives in to confirmation bias at some point, as their expectations are met and they inaccurately conclude that they “knew” something was going to happen. There are very few things in life that we know – the rest is different levels of speculation.

A lot of people speculated that the Mariners offense was going to struggle to score runs before the season began. That speculation may be founded on logical principles, with evidence to support it, and it may even be correct. However, looking at any small sample of data and deciding that it is “real” because it conforms to what you believed before it happened is simply faulty, and underestimates the uncertainty that was involved (or should have been involved) in your original thinking.

People do this all the time, and it causes them to make poor decisions. We simply do not have the ability to forecast the future with certainty, so we have to leave room for the fact that our forecasts could be wrong. When you decide that eight games is early enough to say that this team can’t score enough runs to win because you believed that was true a week ago and this simply validates your opinion, you aren’t building enough uncertainty into your forecast.

This isn’t to single out anyone – I’m just using the lack of offense as an example. I could use Rob Johnson’s constant dropping of the ball as a similar example. Because he was so frustrating to watch at times last year, there’s a preconceived notion that he can’t catch the baseball, so things like his dropped third strike on Gabe Gross last night get magnified, because it lined up with what we already believed. There’s confirmation bias everywhere in life. It’s just something we have to recognize and attempt to adjust for, because if we don’t, we’ll make bad predictions and end up overreacting to recent events.


52 Responses to “Confirmation Bias”

  1. Liam on April 15th, 2010 3:33 pm

    Jon S.

    Here’s a recent post at Fangraphs about this after Vernon Wells hit 3 HRs in his first 8 PAs.

  2. Carson on April 21st, 2010 1:22 pm

    Saving this here for the next time I need an example of confirmation bias.

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