The Impact of Puck Possession and Location on Ice Hockey Strategy
The author followed the Harvard varsity hockey team for a season and recorded some terrific data on possession and zone changes during 5v5 hockey. He then related these to goals scored.
This meshes extremely well with NHL data, but gives a finer look at the 'hows'. In terms of strategy, he found that 'dump and chase' was equivalent to carrying it over the blue line going forward (in terms of expected +/-), and that the same holds true for chipping the puck out of your own end, as opposed to trying to pass/skate it out. This suggests that the ivy league is well coached, and that the players, on the whole, are staying within their roles and abilities (this is my conclusion on the strategy matter, not his).
You can skim over the mathy bits if that's not your thing, as they aren't particularly important. The general idea of still keeping events on the board, even after others have happened ... that's very wise. So if a team gets the puck into the offensive end, and then takes a shot and loses possession, forces the defender into lobbing it back into the neutral zone ... etc, etc ... and a goal is scored 32 seconds later. He would be counting forward from every event to the goal (or to no goal if none were there), as far as 40 seconds. The thinking being that one event (such as getting offensive zone possession) affects the myriad possibilities to come, even if the chain of events doesn't point to that play directly or intuitively.
That's called a Semi-Markov process. Which would make Roger Neilson's stuff from 20 years ago Benjamin Button Semi-Markov (BBSM), where he was looking at the scoring chances and working back through time. The acronym would be better if Brad Pitt's character had been named Benjamin Dutton, but you can't have everything. In fact I would guess that there are only a couple of degrees of separation from Neilson to the person who advised this author on the methodology (the Harvard coach or video coach, maybe? Or an alumni from the professional coaching fraternity?). In any case, by and large he's looking at the right things here. Terrific stuff.
A strict Markov chain is different in that it makes one event alter the nature of the future events, disregarding the events that preceded it. Such as when the score in a hockey game changes from tied to a one goal lead in the early third period ... conventional coaching strategy causes the expected number of total scoring chances to drop from that point forward, and the probability of the trailing team outchancing increases. The score from the first period doesn't affect this a fig, that's the distinction. Or at least that's the way I understand the Markov and Semi-Markov chains. The way of thinking is more important than it's name, in any case.
There is much to be gleaned from this, but the big apple near the bottom of the tree is faceoff data, so I'll grab just it for now. Starting in your own end is a killer; even if you win the draw (much better than losing it, obviously) the prognosis isn't good for the rest of the shift. We all know that I think, but this puts a 'how' with a 'how much'. And the 'how much' is spot on the same for the NHL, or at least for the first half of 07/08, which is all that I checked it against.
Interesting to note also that he acknowledges George Lindsey, an amateur baseball stats pioneer in the 1960s, for his advice. Lindsey's work in baseball is rudimentary by comparison, though it makes me wonder if he would have gone this route with his analysis if he had stuck with his baseball stats hobby. It would have been a monumental task if he had taken it on, baseball is complex.