Not-So-Advanced Stats: An Introduction To “Fancystats” For Wild Fans
By Ger Devine
-PDO-
First off, don’t be scared by the name. It sounds fancy, but it was just the name of a blog commenter who came-up with the concept. PDO, if you want to break it right down, measures “luck”.
According to Eyes On The Prize:
"“PDO is a statistic that’s used to determine whether a player or team’s performance over a set sample is sustainable. The way that this is accomplished is by taking two relatively stable statistics, even strength on-ice shooting percentage and even strength on-ice save percentage, and adding them together.”"
It can be used at a team level or for individual players. It generally works better for analysing a team, as there are more variables and smaller sample sizes for individuals.
The average PDO in the NHL is 1000, so a team/player with a PDO lower then 1000 can be expected to improve their/his EVSV% and EVSH% over time and a team/player with a PDO higher then 1000 can expect their/his EVSV% and EVSH% to get worse over time (this is a concept called progression/regression to the mean, depending on what side of “even” you’re on). The use of the number 1000 can be a bit confusing as we usually see SV% as a three number decimal and SH% as a three digit percentage. For PDO, we just use a three digit decimal for both.
The best example of PDO at work that I can think of is, in 11-12, during the first half of the season, the Wild (with a PDO far North of 1000) shot to the top of the Western Conference, while the LA Kings (with a PDO far South of 1000) languished at the bottom. Then the Wild regressed towards the mean, while the Kings progressed towards it, and, lo and behold, the Kings made the playoffs and won the Stanley Cup, while the Wild plummeted to the nether-regions of the West.
Here’s a good quote on PDO from Fear The Fin last August:
"Even a team that manages a massive 1040 PDO over a 1500-shot sample should expect to see that total regress to the mean by about 90% over the rest of their schedule, meaning they’d most likely post a 1004 PDO over their next 1500 shots. Similarly, a team with a ridiculously low 960 PDO through 1500 shots would likely be a 996 PDO team over the remainder of their season. These are extreme examples to be sure, as teams rarely post PDOs that high or low over any significant portion of the year, but they help to illustrate that regardless of how confident you are in a team’s ability to sustain a PDO substantially higher or lower than 1000, it’s usually a bad idea to bet on it. With the level of cap-induced parity in the NHL, the spread in shooting and saving talent between teams is small and vastly overstated by what we observe in the short run. Some teams with legitimately great (Boston, Vancouver) or legitimately awful (Columbus, Toronto) goaltending can be expected to sustain slightly above- or below-average PDOs but the majority of teams, as seen above, regress sharply to the mean."
PDO isn’t always going to work perfectly, but its main job is to highlight outliers, teams/players who are at the extreme end of the scale in having either a very high or very low PDO, and show that they won’t last.
Cam Charron ranks the PDO numbers for each NHL team each month on Nation Network, so keep an eye on that and, around December, see which teams are riding a high PDO, and which ones are riding a low number and you can probably figure out how things will go for them in the 2nd half of the season.
For more on PDO:
–http://blogs.thescore.com/nhl/2013/01/21/pdo-explained/
–http://www.habseyesontheprize.com/2013/7/29/4566716/fancy-stat-summer-school-pdo