All methods
Action Impact
ExperimentalA derived construct without out-of-sample validation - read as informed opinion.
What it means
Credit for every recorded touch by how much it moved the chance of scoring next.
How it's computed
A Markov chain over play-by-play states; each event is credited with the change in expected goals.
What's validated - and what's not
A descriptive model with no out-of-sample validation. It tracks points closely, so read it as context on how value was created - not as a hidden-value detector.
Coverage
2007-08 on; 2007-09 play-by-play recorded shots on goal only, so those seasons are thinner.
Provenance
Routley, “A Markov Game Model for Valuing Player Actions in Ice Hockey” (2015).
Our Markov chain over play-by-play states. Descriptive - no out-of-sample validation; it tracks points closely.
Our research ledger - every source we tested, adopted, or rejected →Tiers are a promise, not a style. Reconciled is checked against the official NHL record; Validated is tested on data the model never fit; Experimental is a derived construct without out-of-sample validation - read it as informed opinion. When in doubt we take the lower tier.