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flipped r values
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devinpleuler committed Mar 3, 2022
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Expand Up @@ -74,6 +74,6 @@ However, I am confident that `(Naive PSxG - xG) / shot` is considerably more sta

To briefly explain the methodology: for every qualifying player, I've taken their n shots, shuffled them, and split them into two equally sized samples. In the visual, I've plotted the mean residuals in each sample across each other.

If it isn't already clear, the naive approach provides considerably more stability – where the traditional approach, as alluded to above, has practically no repeatability (`r_values = 0.03, 0.57`). For certain use cases, this Naive approach to Post-Shot Expected Goals provides the best of both worlds: the model precision of PSxG without sacrificing the player-level stability of xG.
If it isn't already clear, the naive approach provides considerably more stability – where the traditional approach, as alluded to above, has practically no repeatability (`r_values = 0.57 & 0.03`). For certain use cases, this Naive approach to Post-Shot Expected Goals provides the best of both worlds: the model precision of PSxG without sacrificing the player-level stability of xG.

There remains a lot of room for improvement here, but I think this is compelling evidence that this sort of modelling approach may prove fruitful for better understanding underlying finishing ability.

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