ACTA DOWN THE LINE trap handicapping ALGORITHM
Introduction and Guiding Principles
When we at MCMS designed our algorithm to achieve the ACTA requirements we did so with the following key objectives in mind:
- to minimise the data needed to allow it to calculate, thus reducing the administrative burden on club volunteers
- to maximise the acceptance of the outputs (ie handicaps) calculated by the algorithm by using a data driven approach to inputs and parameter setting
The MCMS handicap algorithm has been designed to increase the difficulty level for those participating in a handicap event to the extent that the likelihood of all shooters shooting the highest score (NB the highest score is not necessarily the possible) in the event is roughly equal. It does not indicate the likelihood of them winning the event, simply the likely score they will shoot in the event. This means that only event scores are considered (not shoot-off scores or wins).
As participants in handicap events shoot under different conditions each time their handicap changes (ie they shoot from a different meterage) a different methodology to the grading algorithm was required. This means that instead of every score triggering a review a minimum number of targets is required to be shot before a review will be triggered. It also means scores will be aggregated rather than percentages averaged due to the lower number of available scores.
To ensure the statistical relevance and comparability of scores and maximise the scores available to be reviewed all event scores will be recorded in legs of no more than 30 targets. This means a 50T event will be recorded as two legs of 25T's thus providing two reference scores for the algorithm (the MCMS user interface now enforces this when setting up an event). To ensure comparability any event legs setup with less than 20T's will be ignored by the algorithm.
As it is scores, and only scores, that truly indicate the likelihood of what a shooter will shoot at their next event, it is only scores that are used by the algorithm. This means there are no manual intervention or discretionary aspects to the algorithm. Hence a shooter cannot choose to stay at a handicap nor can a handicapper choose to exclude a particular score. It also means that extraneous factors such as "wins" are not referenced when determining handicap changes for a shooter.
Whilst a shooter's handicap must be able to move freely over time based on their scores, that movement should be easier when going up and harder when going down. To achieve this the algorithm will require more targets to be shot to move down than to move up.
The algorithm will automatically exclude non-indicative scores. To facilitate this exclusion the algorithm will use a standard cut-off percentage of 72% (eg 18 out of 25). Any scores below this level will be automatically excluded as non-indicative as they are "below the floor".
Handicap Review Based on Scores
Handicap shooting by its nature results in a shooter having a series of scores that are shot at different meterages. The algorithm identifies which meterages the shooter has either proven they can shot at or proven they can't shoot at. Given the limited number of handicap scores that are available the algorithm uses a shooter's trap grade to jump them up to a higher meterage even where they may not have had the opportunity to prove themselves at the lower meterage.
A shooter can "prove" themselves at a meterage by shooting 100 targets at that meterage with an aggregate percentage of greater than 90% (eg 23/25, 22/25, 23/25, 22/25). To ensure the results relevance to the shooter's current ability those 100 targets can only be drawn from within their most recent 150 targets.
Once a shooter has "proven" themselves at a meterage they can only shoot at a meterage lower than the proven meterage via a "downgrade" event. A downgrade event is one where the shooter shoots two consecutive brackets of 150 targets where the best 100 targets within each of those brackets has an aggregate percentage of less than 90% (eg 22/25, 22/25, 22/25, 22/25, 22/25, 22/25). If at any point the shooter "re-proves" themselves at a meterage before meeting the 300T downgrade requirement they must shoot a further 300 targets after the "prove" event to be downgraded.
In order to achieve the objective of giving every shooter a roughly equal chance of shooting the highest score in a handicap event a shooter will be forced to shoot at a higher meterage where they have an "earn" event at a lower meterage. A shooter can "earn" an upgrade to a 1m higher meterage in one of two ways:
- Firstly they can shoot 100% in consecutive legs within a single event whose possibles add to at least 50 targets (eg 25/25+25/25 or 20/20+20/20+20/20) [otherwise known as "50 Straight"]
- Secondly they can shoot 100 targets with an aggregate percentage of 97% or greater (eg 24/25, 24/25, 25/25, 24/25). To ensure the results relevance to the shooter's current ability those 100 targets can only be drawn from within their most recent 150 targets.
Impact of a Shooter's Trap Grade on their Handicap
As significantly more common mark events are shot than handicap events it is possible for a shooter to have a higher ability than they have been able to "prove" through their handicap scores as they have simply not had the opportunity to shoot sufficient handicap events.
To address this and achieve the objective of giving every shooter a roughly equal chance of shooting the highest score in a handicap event a shooter will be forced to shoot at the benchmark meterage for their grade unless they have proven they can shoot at a higher meterage or they have proven they are unable to be competitive at the benchmark meterage.
The currently agreed benchmark's based on trap grades are:
- AA 21m
- A 19m
- B 17m
- C 15m
The effect of this can be shown in the following examples:
- if I am a C grader with no handicap "events" (prove or earn) I will shoot off 15m
- if I shoot 50 straight I will be moved to 16m
- if I regrade to B grade I will shoot off 17m
- if I regrade to C grade before I have "proven" myself at 17m (ie by shooting 100 targets at greater than 90%) I will drop back to 16m as I have earned from 15m so that event remains and my grade downgrade will only bring me back to my lowest proven meterage (which is not necessarily the benchmark meterage for my grade)
- if I am a B grader with no handicap "events" (prove or earn) I will shoot off 17m
- if I regrade to A grade I will shoot off 19m
- if I shoot 100 targets at 90% or more at 19m I will have "proven" my ability at 19m
- If I subsequently regrade to B grade I will continue to shoot at 19m as I have proven myself at a meterage greater than the benchmark for my new grade
- If I am a AA grader with no handicap "events" (prove or earn) I will shoot off 21m
- if I shoot two consecutive brackets of 150 targets where the best 100 targets in each has an aggregate percentage of less than 90% I will shoot off 20m
- if I regrade to A grade I will shoot off 19m as I have not "proven" myself at above the benchmark meterage
- If I regrade back to AA grade I will shoot off 20m as I have proven I can't shoot off 21m so I can't get back there unless I "earn" it through a 50 straight or 100T at greater than 97% off 20m
What about the best of the best?
There are some shooters out there who can continually shoot well off the farthest physical mark of 25m (not me unfortunately!). To recognise this achievement and to make it more difficult for them to move forward to a closer physical meterage the algorithm will allow their "earn" events to push them beyond 25m. Whilst they will continue to physically shoot off 25m their handicap will be recorded at a higher meterage (eg 28m).
This would mean that someone who had three earn events whilst shooting off 25m would be recorded with a handicap of 28m. This would mean they would have to shoot 1200 consecutive targets where the best 100 targets in each bracket of 150 targets had an aggregate percentage less than 90% before they would have to physically shoot off 24m.
It will also make interesting reading to see who can achieve the highest meterage in the country!
Where can I view my calculated handicap?
Once fully deployed your handicap calculation will be available within the MCMS Shooter's app in the "ME" section.
We will look to deploy an interim solution shortly to help people understand how the algorithm will work based on the data currently held within MCMS BUT the ACTA have requested that all shooter's start 2022 based on the data held in their membership system and only reference scores shot in 2022 onwards.
Frequently Asked Questions
Can I request to stay at a meterage?
No. There are no discretionary elements (from the shooter or the handicapper) within the algorithm. Only your scores (and in limited circumstances your grade) will influence your handicap.
Will “AA Elite” remain?
We understand that as a recognition concept it will remain, but this is a question for the ACTA. Within the MCMS algorithm your handicap will be based on the scores you shoot so whether you reached a particular handicap in the past is irrelevant to what your current handicap is.
Why can I have a handicap below my grade's benchmark?
Your grade is an indication of your ability to shoot at 15m. However, given the limited amount of handicap shooting that occurs we use grade changes as a proxy of your handicap ability until you have had the opportunity to shoot enough handicap targets to "prove" your ability at a given meterage.
Therefore where your handicap scores show that you are non-competitive at a certain meterage your handicap should be able to continue to fall to a level that allows you to be competitive (ie where you can regularly score between 90% and 97%) without hitting artificial barriers created by your 15m grade.
What handicap will I start 2022 on?
At midnight on the 31st of December 2021 we will load your handicap as recorded in the ACTA membership database into the algorithm.
We will then run the MCMS grading algorithm. If the run of the grading algorithm results in a grade whose benchmark is different to your handicap as held within the ACTA then your handicap will be updated in line with the MCMS handicap algorithm rules.
This means if you are recorded as A19 within the ACTA system and the MCMS grading algorithm calculates you as AA you will move to AA21. If the ACTA has you as AA22 and the MCMS grading algorithm calculates you as AA you will remain at AA22, if it calculates you as A you will move to A22 (as your "earned" meterage will be retained).
The below table is illustrative of how the algorithm will work.
In the first section it took the shooter 150 targets to achieve a 90% for the best 100 targets of their most recent 150 targets and thus "prove" themselves at 19m (thus locking in 19m even if they regraded to B grade). You can see where they shot two scores below the floor and these were excluded from the calculation.
The shooter then went on to shoot scores that continued to "prove" 19m (the impact being any downgrade calculation had to involve 300 targets after the prove event thus delaying when the shooter could potentially lose a meter). Eventually the shooter strung together a set of 6 scores where the best 100 targets was 97% and thus they "earned" a meter and now have to shoot off 20m.
The shooter then started shooting off 20m but was downgraded to B grade. As the shooter has already proven themselves at 19m and earned their way to 20m they remained on 20m and this remained when the regraded back to A grade.
Eventually the shooter shot 150T at 20m where the scores were above the floor and the best 100T of the 150T's shot was still below 90%. As a result they dropped to 19.5m but continued to physically shoot off 20m. The shooter then shot another bad score but as there was not 150T's shot since the last downgrade event there was no change to the shooter's handicap.
The shooter then regained their mojo and shot two good scores which meant a best 100T out of the previous 150T were above 90% so they "proved" themselves at 20m which eliminated the lost half meter and put them back on 20m. They then shot two more good scores which then resulted in a 100T outcome of 97% and therefore earned them a meter so they now have to shoot of 21m.
Unfortunately the shooter could not get their head around shooting from 21m and had a run of 12 bad scores even though they were shooting well off 15m and got regraded into AA! At the end of the 12 scores they had had two half meter downgrades so they had to go back to shooting off 20m despite being in AA with the hope that they would be competitive off 20m.
The shooter was then downgraded to A grade but as they had previously proven themselves at 20m they could go no lower than 20m and therefore became an A20m shooter. They then sorted themselves out and got back into AA but as their last scores at 21m resulted in a downgrade they have to remain at 20m until they can earn their way back to 21m.