From Alan Ryder’s Ten Laws of Hockey Analytics:
One important warning – do not confuse correlation with causation. The former is easy to prove, the latter is quite challenging. For example, carry-in zone entries yield more scoring chances than do dump-in zone entries. But this could mean that a carry-in is evidence of better neutral zone puck control rather than a cause of better offensive zone puck control.
Which of these variables do you think is the best predictor of playoff series winners in the NHL between 1984 and 1990? In other words, if you were betting on matchups back then and could only look up one stat for each team to influence your decision, which is the one that would most frequently point to the eventual victor?
- Goals For
- Goals Against
- Shot Differential
- Team Shooting Percentage
- Ratio of Shorthanded Goals For vs. Against
It’s gotta be #3, right, based on what we know about the importance of possession? Or maybe #1 or #4, since offence had to be important in a league that was wide open and high-scoring? Or perhaps that old saw about defence winning championships held true, and it was really #2? The one that seems most out of place is #5, a variable measuring rare events that doesn’t take into account anything that happens during the game’s most frequent and important game situation (even strength).
But if we look at the numbers after the jump, we get some surprising results: