Scoring In Bursts: Evidence For In-Game Momentum?

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The notion of momentum gets flung about in sports commentary as if it's some fundamental force, like gravity, that apparently acts at both long and short distances. Teams have - or don't have - momentum for periods as short as a few minutes, for perhaps half a quarter, going into the half-time break, entering the Finals, and sometimes even as they enter a new season, though I think when we start talking about momentum at the macro scale we wander perilously close to confusing it with another fundamental sporting force: form. It's a topic I've addressed, in its various forms, numerous times on MoS.

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Are Some Games Harder to Predict Than Others?

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If you've ever had to enter tips for an office competition where the the sole objective was to predict the winner of each game, you'll intuitively recognise that the winners of some games are inherently harder to predict than others.

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Why AFL Handicap-Adjusted Margins Are Normal : Part II

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In the previous blog on this topic I posited that the Scoring Shot production of a team could be modelled as a Poisson random variable with some predetermined mean, and that the conversion of these Scoring Shots into Goals could be modelled as a BetaBinomial with fixed conversion probability and theta (a spread parameter).

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Why AFL Handicap-Adjusted Game Margins Are Normal

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This week, thanks to Amazon, who replaced my unreadable Kindle copy of David W Miller's Fitting Frequency Distributions: Philosophy and Practice with a dead-tree version that could easily be used as a weapon such is its heft (and assuming you had the strength to wield it), I've been reminded of the importance of motivating my distributional choices with a plausible narrative. It's not good enough, he contends, to find that, say, a Gamma Distribution fits your data set really well, you should be able to explain why it's an appropriate choice from first principles.

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Do Favourites Kick Straighter Than Underdogs?

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We know that the TAB Bookmaker is exceptionally well-calibrated. Teams that he rates 80% chances win about 80% of the time and, more generally, teams that he rates X% chances win about X% of the time. Put another way, teams rated X% chances score more than their opponents X% of the time.

What about other scoring metrics, I wondered?

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Team Scoring Shots and Conversion Rates

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In response to my earlier post on the explained and unexplained portions of game margins, Friend of MatterOfStats, Michael, e-mailed me to suggest that variability in teams' points-scoring per scoring shot - or, equivalently, teams' conversion rates - might usefully be explored as a source of unexplained variability. 

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Explaining Variability in Game Margins

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Some seasons are notable for the large number of blowout victories they force us to endure - a few recent seasons come immediately to mind - while others are more memorable because of their highly competitive nature. To what extent, I've often wondered, could we attribute a season full of sizable victory margins to the fact that strong teams were more often facing weak teams, making the magnitude of the defeats predictable if still lamentable, versus instead attributing them to on-the-day or random events that were genuinely unforeseeable pre-game?

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Home Team and Away Team Scores Across VFL/AFL History

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About 18 months ago I investigated the statistical properties of home teams' and away teams' scoring behaviour over the period from the start of the 2006 season to the middle of the 2012 season taken as a whole. In that blog, using the VGAM package, I found that the Normal distribution provided a reasonable fit to the scores of Home teams and a much better fit to the scores of Away teams over that entire period.

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The Ten Most Surprising Things I've Learned About AFL So Far

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The last few months have been a generally reflective time for me, and with my decision to leave unchanged the core of MAFL algorithms for 2014 I've been focussing some of that reflection on the eight full seasons I've now spent analysing and predicting AFL results.

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Prime Motivation: An Analysis of Prime Numbers in AFL Scoring

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Earlier this week, the TED talk of Australian radio broadcaster, comedian and self-confessed number geek Adam Spencer was posted online. In it he explains his fascination with prime numbers, in particular the discovery of "monster primes", which got me to wondering about the prevalence of prime numbers amongst football scores.
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Is Class More or Less Important In AFL Finals?

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You'll hear it said about sport that class emerges when it's needed most. If that applies to football then you'd expect that better teams would be more likely to win games in the Finals than they are games in the regular home-and-away season.
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Defensive and Offensive Abilities : Do They Persist Across Seasons?

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In the previous blog we reviewed the relationship between teams' winning percentages in one season and their winning percentages in subsequent seasons. We found that the relationship was moderate to strong from one season to the next and then tapered off fairly quickly over the course of the next couple of seasons so that, by the time a season was three years distant, it told us relatively little about a team's likely winning percentage. There is, of course, an inextricable link between winning and scoring, and in this blog we'll investigate the temporal relationships in teams' scoring in much the same way as we investigated the temporal relationships in teams' winning in that previous blog.
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What Do Seasons Past Tell Us About Seasons Present?

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I've looked before at the consistency in the winning records of teams across seasons but I've not previously reported the results in any great detail. For today's blog I've stitched together the end of season home-and-away ladders for every year from 1897 to 2012, which has allowed me to create a complete time series of the performances for every team that's ever played.
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How Many Quarters Will the Home Team Win?

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In this last of a series of posts on creating estimates for teams' chances of winning portions of an AFL game I'll be comparing a statistical model of the Home Team's probability of winning 0, 1, 2, 3 or all 4 quarters with the heuristically-derived model used in the most-recent post.
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