How Does This Work, Anyway?
A.K.A.: “Why is my favorite team ranked lower than a team they beat? This is terrible and you, by extension, are terrible.”
Here’s how this works.
The Heal Points are a time-honored tradition in Maine high school sports, and for good reason. In a state as large as Maine with such a range in school sizes (and driving distances!), you aren’t going to be able to play a balanced schedule within your division. Enter the Heal Points, which are a vast improvement over a simple Won-Loss record.
The thing is, they don’t go nearly far enough.
So I tore them down and rebuilt them on the same framework, only with newer features, like adjustments for where the game was played. For a primer on how Heals work, go here: http://www.bangornorth.com/how-to-calculating-those-mysterious-heal-points/
The old Preliminary Index system (PI) is the biggest flaw of the Heals. The points are solely based on the class of the team you beat, which is essentially the same thing as basing it on the price of gas in that town. There’s not a single basketball reason for your PI. Yes, you get points for a win, but you get the same number of points for beating the best team in your class as you do for beating the worst. That’s absurd.
Luckily, it doesn’t directly affect your final rating, so that allows some liberties.
The new, 5-class system has a weight of 2 points between classes, but we’re keeping the old 5 point difference, with a twist. Each team is placed on a 10-point range, based on their overall ranking (it’s a bit circular, I know, but since it doesn’t directly affect that rating, it more or less works and it’s the best system I’ve come up with). It looks a little like this:
So the best team in Class A is worth the same as an average AA school. The worst team in B is worth the same as the best team in class D. And so on.
This is the part that slows down the Excel file the most.
To that we then apply a Pythagorean Expectation, which was invented by Bill James and adapted for basketball by Daryl Morey. It’s used by a lot of rating systems in a lot of sports.
Win% = (Points Scored)^x / ((Points Scored)^x + (Points Allowed)^x)
So if you play a team in Class B with a weight of 33 (to pick a random number) and you get a Win% of 82%, your PI will be credited 27.06. Beat a better team (say, 37) and you get 30.34. Then that is added all together and divided by the number of games on the schedule.
That’s your mPI. Simple, right?
Of course, this means more to the teams you play. You care about your Heal Points.
Home Court Advantage
First, we need to adjust every game for Home Court Advantage. There’s a lot of theories on how much weight HCA has, and it probably varies from location to location. Some gyms are just harder to play in than others and some fan bases travel much better than others. But, in the 2014-15 season, Home Court was worth, on average, 4.3 points state-wide. So, until a better number presents itself, I’m using 4.5. This means if you win by 10 on the road, it adjusts that to a 14.5 point win on a neutral floor. Lose by 10 on the road and it’s a 5.5 point loss.
Now that we’ve got a HCA on the game, we apply the Pythag on it. Let’s look at a sample game from this season.
On January 2, Brunswick beat Kennebunk 53-45 on the road. In calculating Brunswick’s numbers, we adjust that to 57.5-45. Throw it in the Pythag and we get a Win% of 87.7% (meaning that, based solely on this piece of information, we would expect Brunswick to beat Kennebunk 87.7% of the time on a neutral floor. But 12.3% of the time, Kennebunk would win. Because upsets are wonderful.) Kennebunk currently has a PI of 10.415, so this win netted Brunswick 9.130 points toward the mHeals. We then add that to all the other results, divide by the games on Brunswick’s schedule, and multiply it by 10.
And that’s more or less it.
See? Not that scary.
Glossary of Terms
mHeal: Modified Heals. The main number. The important one.
mPI: Modified Preliminary Index. See above.
eWins: Expected wins. The number of games a team should have won, assuming their luck breaks even.
Diff: Points scored minus points allowed.
SOS: Strength of Schedule. A simple average of the mPI of every team you play
2Play: The strength of your remaining schedule
%Heals (or mHeals Converted): The percentage of available mHeals you’ve had available to you that you’ve actually earned. The formula is mHeal/(mPI * G)
%Heals v Top 50: Same idea, only counting just the games against teams in the Top 50.
Win%: The Win Expectation for a game. See above.