Friday, February 19, 2010

Streakers, chaotics, and hypocrites

In the previous post, I examined the relationship between pickup percentage, (percentage of spare chances converted) to strike percentage (the percent of strike opportunities converted) to see if improvement in bowling comes with improvement in both facets of the game. Afterward, I thought it might be interesting to look at these data as time series, or to examine how pickup % and strike % have changed over time for the Movements. I found some unexpected things.

For this analysis, I used a 10 week moving average, one of my favorite tools for gauging change in skill in bowling. Let's start with the data for our cleanup man, JD. Below on the left are Joe's time series for strike and pickup %. Notice that he has been slowly improving in both aspects of his game over the course of the season with a few hiccups, like the one he is currently experiencing. He peaked back on the 11th of January, and based on last week, he may be heading back in the right direction. If you take the dots that make up each of these curves and compare them directly, you find that there is a strong positive relationship. This means that when Joe is feeling it, he is feeling it in all aspects of his game. When he is getting a lot of strikes, he is also picking up his spares. Also, when the strike game is not there, the second ball is absent as well. I should note that he has made HUGE strides in both aspects of his game this season, perhaps due to his ball change.

In comparison, Johnebob and the Rookie show a second type of pattern. In both cases, there is no relationship between pickup and strike %. This means that they operate independently, or that some nights the strikes are there, sometimes not. Some nights the spare game is there, sometimes not. But there is no relationship whatsoever between the two.

For a third type of pattern, you have to look at my trend below. The curves seem to symmetrically oppose one another. If am improving in strikes, I am getting worse at spares. If my spare game is coming around, my strike game is slipping. In fact, when you compare the two directly (below right), that is exactly what's going on. It suggests that over the last year or so, I have always been improving at one aspect of my game while getting worse at another. I've been going nowhere fast.

So here you have three different types of bowlers. I'll call the first the "streaker" because they are streaky. When the strike game is on, so is the spare game. When one is off, so is the other. This will result in dramatic and streaky changes in game scores from week to week. Johnebob and Gingy could be called "chaotics" because there is nothing predictable about the relationship between their ability to throw the first ball and second. As for me, I should be called a "hypocrite" for constantly contradicting different aspects of my game and making little progress as a consequence.

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