Advanced Hockey Statistics
"What questions does it answer?"
There are a number of new statistics that have been developed over the past few years (i.e. since about 2007) that have helped analysts and fans to better understand the game. What follows is a brief overview of these statistics.
Corsi and Fenwick
Corsi and Fenwick are similar to the traditional +/- stat, but instead of goals it is based on shots. They attempt to answer the question, "Who is controlling possession of the puck?". Because there aren't possession stats in hockey (yet?) we instead use shots as a proxy, which has been shown to correlate well with puck possession. This can be presented as a +/- stat (i.e. total shots for - total shots against) or as a percentage (i.e. total shots for / (total shots for + total shots against)).
Corsi For (CF) = Shots + Misses + Blocks Against
Corsi Against (CA) = Shots Against + Misses Against + Blocks For
Corsi For % (CF%) = CF / (CF + CA)
Corsi = CF - CA
Fenwick is essentially the same as Corsi, but it excludes blocked shots.
While Corsi and Fenwick count shot attempts, they don't account for quality of the shot. Expected +/- considers the shot location, and uses league-wide averages to determine the likelihood of that shot being a goal. It doesn't factor in whether the shot actually resulted in a goal or not. Instead, it's giving a sense of shot quality by looking at the odds of scoring a goal from that location.