Soccer analysts are big fans of correlations. Whenever one of us brings out a new metric, we usually quote some correlations to show how “good” it is. But these correlations can be meaningless or, worse, misleading. Here’s what to look for. As I’ve written before, most soccer metrics ought to be correlated with winning or with some other objective – perhaps a style of play or avoidance of injury – that is important to the team. Here, for simplicity, I’ll stick with one version of winning: attaining the highest possible position in the league table at the end of the…
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It’s no surprise that Mesut Özil, Arsenal’s mercurial playmaker, has been grabbing the headlines. He has 10 assists after featuring in just 11 matches, and he’s the new owner of the Premier League’s record for consecutive matches with an assist. But a closer look at his statistics shows that he may be starting to go downhill – albeit from a very high peak. If Özil’s only job were to assist goals, then there’d be no point writing this post. His real job, though, is to make Arsenal better than anyone else would at the same position on the field. That…
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One of the biggest and most important challenges in sports analytics is asking the right question. Many metrics are produced and published without any sense of how precise they are, what assumptions they rely on, and how they might be used in practice. As a result, it’s hard to phrase questions that the metrics can answer correctly, at least from a statistical point of view. Shooting and saving skill are cases in point. Recently Michael Caley, one of the best soccer analysts doing public work, suggested an approach to measuring shooting skill. Like others before him, he chose to focus…
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