Puck Puzzlements
January 8, 2011 2:09 PM   Subscribe

Hockey questions: How do statisticians keep track of every single player's time on ice, as well as plus/minus, shots, takeaways, giveaways, secondary assists, etc? This question could also apply to other sports, eg basketball ("Wait, who got the assist on that shot?") And how do coaches keep track of players' cumulative time on ice during the course of a game, and prevent tiring them near the end of it?

Top players' TOI per game can be remarkably consistent. Are the asst coaches assigned to keep track of certain lines/pairings? Presumably they'll know going into the 3rd period how many minutes a guy has left, but still, it seems hard with players constantly skating on and off, special teams situations, and some having to go on out of order because they're defensive matchups guys, or faceoff specialists.

And do the statisticians ever rely on instant replay to check on minor stats like shots or plus-minus? I know they'll do it to see who should get credited with a goal.
posted by TheSecretDecoderRing to Sports, Hobbies, & Recreation (9 answers total) 5 users marked this as a favorite
 
The league has statisticians collecting information in real time as the game occurs. Then everyone works off those official stats.

I had a friend who did this for MLB for a while. Him and a few others sat there with lap-tops taking tons of notes as they watched the game. He did pitching stats - strikes, balls, speed, pitch count, and more. He had a set of things to keep track of. He would get a really good seat in the stadium (mostly north-east stadiums), and sit there watching the game, and getting paid to take notes. It was not a particularly high paying job, but he loved it.
posted by Flood at 2:21 PM on January 8, 2011 [1 favorite]


This does not have to do with hockey but is likely indicative of the observational skills required to keep stats for sports. When I was in college, there was a 1-credit "course" on keeping tennis stats during a match. I was surprised to find out there was a special machine (I am sure it's different now) but it had many many unique buttons on it for each and every type of shot, placement, shot success, etc. The ultimate goal was that you'd be able to keep your eye completely on the action and press the corresponding buttons without looking. For me it was like typing after just learning the alphabet and seeing a keyboard for the first time. In any case, it's likely there's not only multiple observers keeping stats but there's probably a special software and interface for it.
posted by thorny at 2:55 PM on January 8, 2011


Unfortunately, statisticians in the NBA are often retained for a specific team and may "fudge" certain numbers, as you can read about here.
posted by kuanes at 3:46 PM on January 8, 2011


I always assumed that it was partly the video coach keeping the coach appraised and partly coaches being able to recognize the player's fatigue level and shifting them appropriately. 20-some minutes is probably the most a forward can play before they start showing fatigue so if the coaches is trying to get top-liners out as much as possible without getting them too tired it probably works itself out.
posted by ghharr at 4:47 PM on January 8, 2011


Check out this article from The Hockey Writers website "The NHL Officials You Don't See", all about the people who keep NHL stats: Part 1 Part 2
posted by BozoBurgerBonanza at 5:21 PM on January 8, 2011 [5 favorites]


In the early 90's, there was a company in our building that was working on a computerized system for keeping track of ice time, shots on goal, and maybe a few other things. One of the guys there described the system that it was going to replace.

The old system had an electric clock for each player, and a long row of switches underneath, one for each clock. Every time there was a line change, the guy in charge of tracking ice time would mash all the switches to the off position, then quickly turn on the ones for the players currently on the ice.

So the idea there was that each clock only ran when its switch was on, and at the end of the game you could just read off the minutes elapsed on each clock and that'd give you the ice time for every player.

The guy I was talking to was trying to come up with something that intuitive for use on a laptop. For tracking shots on goal and so on, he said it was working out so that they really needed a second person for that, with a different UI available, e.g. click on player number, click on location of the shot. And all this was just for one team.

I don't know if this particular company was ever successful in selling their product, and I don't know what has happened in the last 20-ish years in this field.
posted by FishBike at 6:03 PM on January 8, 2011


Top players' TOI per game can be remarkably consistent. Are the asst coaches assigned to keep track of certain lines/pairings? Presumably they'll know going into the 3rd period how many minutes a guy has left, but still, it seems hard with players constantly skating on and off, special teams situations, and some having to go on out of order because they're defensive matchups guys, or faceoff specialists.

There isn't amount of minutes a "guy has left." The TOI for the same guys is just usually consistent because coaches play their lines so similarly and the same things generally happen every game (e.g. short handed a few times, have a few powerplays)
The players are in charge of knowing who they are going on for and the coach generally relays this information. Some coaches have their assistant coach take charge of the defensive changes while they concentrate on the offense.
Most coaches don't know how long their players have been playing though. Only some very anal coaches actually time every line change (see Detroit, 45 seconds). It's the players responsibility in most cases to get themselves off the ice and signal for the change.

And do the statisticians ever rely on instant replay to check on minor stats like shots or plus-minus? I know they'll do it to see who should get credited with a goal.

Usually the only thing that gets changed after the fact is who gets credited with a goal. +/- is pretty hard to mess up.
Shots, hits, takeaways, and giveaways are notorious for being wildly different between different buildings.
And yes, they use replay. The officials in charge all have monitors in arms reach the entire game.

All of the stat keeping is done by NHL off ice officials and it's generally the same team every night for every home team (so 30 sets of 15.)
They get the job done so well because there are about 15 of them and because they are really good at watching hockey. The officials are broken down into 2 goal judges, a game time-keeper, a penalty time-keeper, 2 penalty box attendants, a commercial coordinator, the official scorer, 5 scoring staffers, a video replay judge and a spotter.

For instance, when a goal is scored the referee only signals that the goal has been scored and it's the off ice officials job to determine everything else.

A lot of them have been doing the job for over 15 years.
posted by zephyr_words at 6:31 PM on January 8, 2011


FWIW, every sport that's played at the professional level has software designed for this task. I've seen one for volleyball in action, and it's pretty impressive- it knows after each contact what the next contact might be, and gives the user those options. In a long rally there can be 2-3 pieces of information per second to note, and the software does a great job of keeping the user from falling behind.

I've done the same job on paper and it's difficult to track more than 2 stats per tracker that way.
posted by Four Flavors at 3:22 PM on January 10, 2011


Thanks for the replies. BozoBurger's link came closest to nailing my question.

I do know certain stats can be subjective (announcers talk about "home cooking" for apparently padded stats), and I think even the NHL no longer allows such stats to be used in arbitration hearings because they're so unreliable. And in that regard, kuanes's NBA link was pretty enlightening too. Seems the only time you really hear about the subjectivity of stats is errors in baseball.

The NHL article sounds like it works more or less the same way as the proposed system FishBike mentions. I would've liked a little more specifics though. Once in a blue moon Fox Sports West will run the same game on two channels, with one being the game with no announcer feed, and behind-the-scenes stuff between plays. It'd be nice if they got into this stat stuff, and the software.
posted by TheSecretDecoderRing at 12:44 AM on January 11, 2011


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