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Do NFL Coaches Coach to Win?

Do NFL Coaches Coach to Win?. An examination of the relation between in-game decision making in the NFL and a coach’s job security By Mitch Levy. NFL Rules Background. What are two point conversion attempts? What are fourth down attempts?. Theoretical vs. Actual Strategy.

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Do NFL Coaches Coach to Win?

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  1. Do NFL Coaches Coach to Win? An examination of the relation between in-game decision making in the NFL and a coach’s job security By Mitch Levy

  2. NFL Rules Background • What are two point conversion attempts? • What are fourth down attempts?

  3. Theoretical vs. Actual Strategy • Modeling suggests coaches should attempt these plays more often • ~2.5 times as often for fourth down attempts* • ~5 times as often for two point conversions* *From model by footballcommentary.com

  4. Theories about the Discrepancy • Modeling error • Loss aversion/delaying outcome • Lack of knowledge • Dislike of criticism

  5. Hypotheses • Coaches are aware, that their decisions are suboptimally conventional (but not necessarily the degree) • Non-expected utility theory • Dislike of criticism plays a meaningful role • Stronger incentives to win produce better decisions

  6. Idea of Study • Evaluate coaches with different degrees of job security and see how their decisions change • Hypothesis: coaches with their jobs on their lines will endure more discomfort to win more

  7. Details of Study • Coaches of teams that made the playoffs the previous year will be deemed safe – all other coaches are unsafe • Evaluate conformity to suggestions of Markov model for “safe” vs. “unsafe” coaches

  8. Some Possible Objections • Playoff teams may have better conversion odds • Playoff teams may have better coaches • Playoff teams may have older, more conventional coaches • Non-playoff teams may be worse, and pursue a high-variance strategy

  9. Data Sources • NFL Plays, 2002-2012 (Courtesy of Brian Burke, advancednflstats.com) • Suggestions by model: nflcommentary.com, run by (NAME HERE) • Model is a Markov Chain analysis

  10. Two Point Attempts: Model Info • Input variables: time remaining, score discrepancy • Output variable: probability of success that justifies attempting the two point conversion, rather than kicking an extra point

  11. All Two Point Attempts: Summary • Total Two Point Attempts: 622 • Total Two Point Conversions: 319 • Overall Success Rate: 51.28% • This rate used to determine which conversions should be attempted

  12. 2 Pt. Play, Safe vs. Unsafe Coaches • Safe Coaches: • 159 Attempts, 720 Non-Attempts • Correct attempt rate: 18.1% • Unsafe Coaches: • 331 Attempts, 1212 Non-Attempts • Correct attempt rate: 21.5%

  13. “The Belichick Effect” • Bill Belichick is an outlier, both in appearing in the playoffs 10/11 times in the sample (no other coach appears more than 4 times) and in his aggressiveness. • The numbers, controlling for Belichick, are even more compelling

  14. 2 Pt. Play, Safe vs. Unsafe Coaches, Controlling for the Belichick effect • Safe Coaches: • 141 Attempts, 688 Non-Attempts • Correct attempt rate: 17.0% • Unsafe Coaches: • 328 Attempts, 1205 Non-Attempts • Correct attempt rate: 21.4%

  15. Statistical Significance • Without Belichick Effect? • With Belichick Effect?

  16. Fourth Down Attempts: Model Info • Input variables: time remaining, score discrepancy, position on the field • Output variable: probability of success that justifies attempting the fourth down play, rather than punting or kicking a field goal

  17. Fourth Down Attempts • Conversion success on 4th and ... • 1 : 0.664885088188, 2 : 0.584415584416, 3 : 0.555831265509 • 4 : 0.544668587896, 5 : 0.493710691824, 6 : 0.527659574468 • 7 : 0.492462311558, 8 : 0.436090225564, 9 : 0.485148514851 • 10 : 0.474137931034, 11 : 0.511904761905, 12 : 0.426666666667 • 13 : 0.338461538462, 14 : 0.388888888889, 15 : 0.446153846154

  18. Determining whether a coach “should” attempt a 4th down play • If 4th and 1, use determined value of 0.665 • Otherwise, use 0.61 – 0.015*yds_to_go

  19. 4th Down, Safe vs. Unsafe Coaches • Safe Coaches: • 910 Attempts, 1437 Non-Attempts • Correct attempt rate: 38.8% • Unsafe Coaches: • 1768 Attempts, 2708 Non-Attempts • Correct attempt rate: 39.5%

  20. 4th Down, Safe vs. Unsafe Coaches (Controlling for the Belichick effect) • Safe Coaches: • 859 Attempts, 1377 Non-Attempts • Correct attempt rate: 38.4% • Unsafe Coaches: • 1755 Attempts, 2692 Non-Attempts • Correct attempt rate: 39.5%

  21. Statistical Significance • Without Belichick Effect? • With Belichick Effect?

  22. Implications

  23. Controlling for Offensive Strength • Calculate separate conversion probabilities for playoff, non-playoff teams • Same methodology: separate 4th and 1 probability, linear regression on 4th and 2 through 4th and 15

  24. Controlling for Offensive Strengthon 4th Down Attempts • Safe Coaches: • 882 Attempts, 1429 Non-Attempts • Correct attempt rate: 38.1% • Unsafe Coaches: • 1755 Attempts, 2692 Non-Attempts • Correct attempt rate: 39.5%

  25. Model

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