WPI FAQ

This is everything you need to know about the WPI. Probably more. Please check here first before sending me e-mail with questions about the ratings. It'll save us both time. 

In the 2000-2001 season the WPI formula was changed to 33%-33%-33%. In the first year (1999-2000) the formula was 25%-50%-25%.  Based on feedback from basketball coaches statewide, the ASAA Board voted to change the formula to lessen the weighting of schedule strength.

 

What? You still want to know more? E-mail your questions to me at dlamprecht@compuserve.com

Last updated 02/04/02

What is the WPI?
The WPI (Winning Percentage Index) is a measure of strength of schedule and how a team does against that schedule. It does not consider things like margin of victory or where a game is played, only whether or not a team won. It is similar to the calculation of the RPI (Ratings Percentage Index) which is used by the NCAA as one of their factors in deciding which teams to invite to the NCAA tournament and where to seed them.

The RPI was created and  is maintained by the NCAA Division I Men's Basketball Committee. They have always placed a premium on schedule strength when selecting teams for the tournament, so they wanted a relatively simple way to measure that and the RPI was born. The WPI models the RPI system and was used for the first time in Alaska to seed the Girls and Boys State 4A Basketball Tournament in March 2000.

How will the WPI be used?

Each region will determine which teams will represent them in the state basketball tournament. This has traditionally been done with a regional basketball tournament. After those teams have been determined by the regions, the WPI will be used as the primary factor in the seeding process. 

What is the formula?

The basic formula is 33% team winning percentage, 33% opponents' average winning percentage, and 33% opponents' opponents' average winning percentage.

For example:

Team A's WPI would be (.33 * 0.8333) + (.33 * .600) + (.33 * .700) = .275 + .198 + .231 = 0.704 

Do you adjust the opponents' average winning percentage to account for the fact that they have played the team in question?

Yes. When you want to see how the opponents of team A have performed, you want to see how they have done against teams other than team A. For example, if the opponents of team A have 50 wins and 30 losses, and team A has a record of 5 wins and 1 loss, then the opponents of team A have 49 wins and 25 losses against teams other than team A.

In the opponents' average winning percentage, do you include the records of teams scheduled in the future?

No. A team's record is included in the opponents' average winning percentage only after the game is played. This is because a team's entire schedule is not usually known, mostly due to games added because of in-season and conference tournaments. Also, sometimes games get cancelled.

If a team plays somebody more than once, is their winning percentage included more than once?

Yes. Once for each time a team plays that opponent.

What other factors are considered in seeding?

When the WPI values are close between two teams, other factors such as big wins, winning record in last part of the season, and first round bracketing between intra-region teams will be considered. Efforts will be made to avoid first round intra-region match-ups, but if the first and eighth seeds are within the same region, there is a higher chance of meeting than if the teams are middle seeds.

What is the Strength of Schedule?

It's 33% of the opponents' winning percentage plus 33% of the  opponents' opponents' winning percentage. It's basically the last two components in the WPI formula. Strength of schedule is 67% of the WPI calculation.

Why do the rankings seem so weird early in the season?

The WPI is primarily a measurement of strength of schedule and how the team did against that schedule. Consequently, the numbers can really be skewed early in the season because teams have played so few games. For example, a team can be 2-0, but its opponents haven't played anyone else yet, so its strength of schedule is 0. That's 67% of the formula, so the team won't be rated very highly. The data starts to take shape and look reasonable as conference play gets into full swing around mid January. And the more games played, the better the data gets.

Which games are counted in the WPI?

Only games against other Alaskan 4A schools. The main reason for omitting outside 4A-5A schools is the availability of those teams' opponents' and especially their opponents' opponents' win loss percentages.

Why is my team ranked behind another team that we beat?

The WPI is a measurement of strength of schedule and how you did against that schedule. The ENTIRE schedule. To look at only one game ignores the "any given day" aspect of sports. In 1998-99, for example, in the NCAA Iowa lost to Creighton, who lost to Drake, who lost to Evansville, who lost to East Carolina, who lost to James Madison, who lost to Maryland-Eastern Shore, who lost to Delaware St, who lost to New Hampshire, who lost to Yale. No one in their right mind would have rated Iowa behind any of those teams, let alone all of them.

Why did my team move up after a loss (or down after a win)? Why did my team move up (or down) when they didn't play?

There could be several reasons. One is that since the WPI measures strength of schedule, so it is possible to have a higher WPI after playing a good team, win or lose. Also, a team could have its WPI move down by playing a bad team, win or lose. A team's WPI can also change when they don't even play if one of the teams on their schedule played.

Another thing is that rankings are relative, meaning that a team's ranking is affected by the results of teams around them in the rankings. A team could move in the rankings without even playing if the teams around them played. This is the way computer models can work and is often the most confusing difference for people used to following polls.

Should I have a strategy to improve my WPI?

First and foremost, win as many games as you can and schedule as many strong teams as possible (that should probably be your strategy anyway). If a team you have on your schedule is playing a team that is not on your schedule, root for the team that's on your schedule (be loyal to and support your region's teams).

 Why are some scores reported as 1-0?

These are games where the winner is known, but the exact score is not since no scores have been reported to ASAA or local newspapers. When coaches see these scores, it should be a reminder that they need to call, fax or email the correct scores into ASAA. The WPI numbers are still calculated correctly since it is based on wins and losses only. Point spread in games against common opponents is one of the factors that are considered in the final seeding decisions when two teams are close in WPI value. So actual scores should always be reported to ASAA.

 Why are some scores reported as 2-0?

These are forfeits.