MNP now uses Individual Player Ratings (IPR) to track the strength of each player, and more importantly to track and balance team strength. The Team Rating is simply the sum of IPR of all players on that team’s roster. An adjusted Team Rating may exist on any specific night when roster players are absent and subs are used. Refer to the Team Roster and Substitute rules for more details on adjusting players on the team.
This page provides the details on the calculation of IPR.
IPR sources two databases of competitive results, namely the IFPA World Rankings, and the Matchplay.events Ratings (MPR). Through Fall 2017, only IFPA world rankings were used, and only to track players ranked in the top 1000. IPR expands the use if IFPA world rankings to track all players, and adds in the MPR that provides a more accurate rating by considering head-to-head data from more events, including Monday Night Pinball matches themselves.
MPR uses the Glicko algorithm that starts every player at 1500, and increases their rating as they win more, or decreased it as they lose more. A Ratings Deviation (RD) specifies the presumed accuracy of the rating, and can range between 125 (not accurate at all) and 30 (as accurate as the algorithm expects to be).
The MPR Lower Bound (MPLB) is computed as a player’s rating minus 2x the lower bound. Thus the lower bound for a new player starts at 1500-250 = 1250. For a player with a rating of 1550, and RD of 30, their lower bound would be 1550-2*30 = 1490. It is this lower bound that is used in the computation of IPR.
MNP retrieves the data from both IFPA and MPR multiple times per season, and produces a current list of all roster players and anyone who has subbed either the prior or current season. For each player, it computes an IPR for each player. Once that is done, the IPR for the player is frozen until the next data retrieval update, even if the player’s MPLB or IFPA changes shortly after the update. MNP will generally announce at least one week ahead of time, and possibly at the start of the season, approximately when each update will occur, allowing captains to plan accordingly.
The IPR itself is a value between 1 and 6, as illustrated in the following diagram:
And IPR of 1 represents a novice, 3 is the average player, and 6 is for the top players in the city. A player’s IPR is computed by comparing the player’s current IFPA ranking and MPLB to defined thresholds, and determining what range they fall in. The ranges are defined so that at the time the IPR list is updated, the lowest rated 15% of roster players are a ‘1’, the next 20% are a ‘2’, the next 30% are a ‘3’, the next 20% are a ‘4’, the top 15% excluding the top 2% are a 5, and the top 2% are a 6. The MPLB of non-roster players (i.e. subs) do not affect the computation of the thresholds, but all not-roster players in the list are still assigned an IPR by where they fall within the range.
The MPLB is the primary assignment of IPR. However, if a player’s IFPA ranking maps to a higher IPR value, then that higher value will be assigned to the player. The use of IFPA ranking is because most major tournaments, including NWPC, NWPAS, Pinburgh, and tournaments in other cities do not currently have their data submitted to MPR. Rather, MPR data primarily consists of the many local weekly and monthly tournaments in the Seattle area. The continued use of IFPA ranking data in this way ensures that a player who typically only plays in the larger IFPA-ranked tournaments, and has demonstrated a high level of performance those tournaments, will still be assigned an appropriate IPR, and won’t show up as a 1 or 2 and appearing as a novice due to lack of MPR data. For the majority of players who play locally more than they play in the major tournaments, the MPLB will be more accurate, and thus that will tend to provide the basis for the IPR.
- Glicko algorithm used by matchplay: http://www.glicko.net/glicko/glicko.pdf
- MP implementation of Glicko (read only): https://github.com/haugstrup/TournamentUtils/blob/master/src/GlickoCalculator.php
- IFPA Ranking Information and Computation: https://www.ifpapinball.com/menu/ranking-info/