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Tuesday, 26 May 2015

Expected v Actual: Conversion Percentages

So, I used Michael Caley's expected goal page and calculated expected shooting%, expected save% and expected PDO. Those calculated percentages can be found in the table below alongside dumb 'ol shooting%, save%, and broad PDO.

 Data

Plonking the actual conversion metric and the relevant expected  metric into a scatter plot churned out some interesting results.

 Actual Sh% v Expected Sh% r2=0.342
Actual Sv% v Expected Sv% r2=0.290
Actual Broad PDO v Expected PDO r2=0.406

 I don't really have an opinion on those r2 scores. It would take a person with more emotional investment in private expected goal models to tell us if those correlations are disappointing or not.

 One weird thing I did notice when running those numbers at week 38: the sh% & PDO correlations are almost twice as strong now as they were just 3 weeks ago at week 35.
Strange, eh. Anyway, the data, as always, is shared below. Kick it around, play with it, bend it break it.
sh% sv% Broad PDO xsh% xsv% xPDO
Arsenal 11.60 91.15 102.76 11.13 91.03 102.16
Aston Villa 7.51 88.31 95.82 9.30 90.40 99.69
Burnley 6.53 91.00 97.53 10.07 90.27 100.34
Chelsea 12.97 92.31 105.27 11.46 92.04 103.50
Crystal Palace 10.71 90.29 100.99 10.05 91.45 101.49
Everton 9.73 90.06 99.79 7.91 90.87 98.78
Hull 7.71 89.80 97.51 8.27 89.52 97.79
Leicester 10.07 90.02 100.08 9.69 89.80 99.49
Liverpool 8.81 88.43 97.25 9.22 90.05 99.27
Man City 12.41 90.16 102.56 10.61 89.64 100.25
Man United 12.13 90.26 102.40 10.18 88.66 98.83
Newcastle 8.55 85.81 94.36 9.27 89.14 98.42
QPR 7.88 88.21 96.09 8.76 89.35 98.12
Southampton 10.67 91.41 102.08 10.95 89.64 100.58
Stoke 9.58 90.11 99.69 9.52 89.78 99.30
Sunderland 7.65 91.52 99.17 9.58 91.94 101.52
Swansea 10.90 91.12 102.02 9.76 90.27 100.03
Tottenham 11.07 89.16 100.23 9.35 88.94 98.29
West Brom 9.20 90.64 99.84 9.49 90.37 99.86
West Ham 9.05 92.01 101.06 10.51 90.37 100.89
LGE AVE 9.89 90.11 100.00 9.75 90.18 99.93



Shooting%

 Size of the bubble is Goals For. Colour of bubble is league position



 Save%
Size of the bubble is Goals Against. Colour of bubble is league position
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