Full Overview of Past Performance Indicators (PPI) - (or ratings)

When you play a board, your PPI may or may not change depending on:

1) are you playing in a room that affects PPI?

2) are you partnering a guest or a full member?

3) What is your expected score based on the PPI of the four players at the table?

4) what is your actual score?

For an up-to date listing of which rooms affect PPI, take a look at “Bridge Rooms Timetable”.

To tell if your partner is a guest or a member, you can lookup their profiles via the index, and if the name appears in red, then they are a guest.

Introduction

Newcomers are assigned an initial P.P.I. of 50%.

Because this initial assignment may not be reliable, boards played when you are partnering Guest Members are excluded from the calculations, unless you are yourself a Guest Member.

For the same reason, your P.P.I. will be seen only after you have played at least 50 qualifying boards

For the calculations, we need to know how many boards had previously been played by each player since the start of the scheme within the qualifying MP rooms only. The start of the scheme was the beginning of July 2002. We also need to know how many qualifying boards have been played by each player in the preceding 90 days.

THE FORMULA

At the end of each event, each player’s P.P.I. is updated. The updating is carried out on a board by board basis and in accordance with the following formula:

A = a + [ p – {(a+b-c-d)/2 + 50}] /m

where

m = 30 if k less than 30,
m = k if k is between 30 and 300
m = 300 if k is greater than 300 and if w is less than 150
m = 2w if k is greater than 300 and if w is between 150 and 300
m = 600 if k is greater than 300 and if w is greater than 300

and where (using Fred as the player for whom we are calculating)

A = Fred’s new P.P.I.

a = Fred’s existing (ie old) P.P.I.

p = The percentage value of Fred’s score on the board (This will be between 0 and 100)

b = Fred’s partner’s existing P.P.I.

c = Fred’s Left Hand Opponent’s existing P.P.I.

d = Fred’s Right Hand Opponent’s existing P.P.I.

k = The number of qualifying boards that had previously been played by Fred since the start of the scheme within rated MP rooms only (except for boards played when partnering Guest Members).

w = The number of qualifying boards that had previously been played by Fred during the previous 3 calendar months within rated MP rooms only (except for boards played when partnering Guest Members). - Updated monthly.

The letter “m” is referred to as the weighting factor. It denotes how much weighting to give your updated P.P.I. for the most recent board that you have played. For many players, the weighting factor is 600 so that the most recent board that you play accounts for one six hundredth (or 0.0167%) of your P.P.I.

However, there are reasons why “m” is not 600 for all players, and this is where all the "k" and “w” stuff come in.

Firstly, new players are artificially assigned an initial P.P.I. of 50% and this can be a long way out, so it's important for the early results to be weighing heavily compared with the limited (or non-existent if he is playing for the first time) "history" of the player. As the player plays more and more boards the weighting factor will gradually increase.

The P.P.I. figure of a newcomer will therefore fluctuate considerably over his first visit or two.

Let's say a newcomer plays at a table where the other three players also have a P.P.I. figure of 50% and over 12 boards the newcomer scores 40% overall. His P.P.I. will go down from 50% to about 46% straight away.

It is because of the unreliability of the initial P.P.I. of a newcomer that partners of guest members will find that such boards played will not count towards their P.P.I.. This is to prevent members being discouraged from partnering guests as a result of this scheme.

A very inexperienced bridge player could easily see their P.P.I. go from 50% to 35% by the time they become a Full Member and then as they gradually become more experienced and a better player, they will see their figure gradually rise up.

In order for the P.P.I. to be more responsive for players who don’t play frequently in the qualifying rooms, whether that be because they play mainly in the IMP or Social rooms, or whether they simply play online infrequently, the weighting of the most recently played qualifying boards will increase for these players.

Thus, there is increased volatility of P.P.I. for those that play less than 300 qualifying boards in 3 months, equivalent to 3 hours a week, or 2 Daily Tourneys a week. Volatility is doubled for those playing fewer than 150 qualifying boards in 3 months, equivalent to about one Daily Tourney or one 14 board session a week.

FOLLOWING YOUR P.P.I.

Unfortunately, it is difficult for members to keep an accurate manual check on the calculations of their P.P.I. figure. This is because of the following factors:

P.P.I. figures are recalculated after an event at the time the event is archived rather than when the event is scored. The timings of this vary. Most events are archived very quickly, but calculations for some tournaments are made sometime after the event.

The use of suit symbols, rather than figures in the profiles of the other players, means that you have only an approximation of the P.P.I. figures for these other players.

Details supplied from anlaysis & support by Barrie Partridge, "Senior Kibitzer" – August 2005