Why Do PDGA “Rating Points Per Stroke” Vary?
, 2022-09-30 10:42:06,
More throws mean less weight on each one.
September 30, 2022 by Chuck Kennedy in News with comments
This is not an official PDGA statement. This analysis was done with ratings data prior to 2019.
Among the many questions players have regarding the PDGA Ratings calculations, this one has popped up again at a recent elite event when Joel Freeman’s exceptional Butler County Disc Golf Classic 14-under par final round came in rated 1077: Why does the ‘rating points per stroke’ (RPPS) get progressively smaller as the course difficulty increases?
The simple mathematical reason is that each throw added to course difficulty or total stroke count will automatically become a smaller percentage of the total strokes a player will throw. We call our course difficulty measurement the Scratch Scoring Average (SSA). This is the score we expect a 1000-rated player or player pool to average. Compare the scoring stats for the two courses shown below.
This course, C54, has 18 holes that average 3 for a 1000-rated player pool making it a course with a 54 SSA. The blue dotted disc on hole 10 shows this player threw 1 stroke less than the SSA. This SSA may not equal par set by the TD.
This course, C72, has 18 holes that average 4 for a 1000-rated pool of players making it a course with a 72 SSA. The blue dotted disc on hole 10 shows this player also threw 1 less than the SSA. Again, this SSA may not equal par set by the TD.
The solid blue or dotted disc for each hole shows the number of shots a player has a reasonable chance to shoot less than 3 or 4, respectively. These are considered potentially “savable” throws. The black discs on each hole show the shots that usually cannot be saved except for the rare ace or eagle. In other words, almost every disc golf hole score will include these “Last 2 Shots” that are not realistically savable.
Once we remove the Last 2 Shots from each hole score, we are left with the number of throws that can potentially be saved as a means to measure a player’s performance. On C54, 18 blue shots can be saved. On C72, 36 blue shots can be saved. So, the value of a player saving one throw on C54 equals 1 throw divided by 18 savable throws. Thus, each throw is worth 1/18=0.056 or 5.6% of the savable throws. On the 18 shots more difficult C72 course, saving one throw equals 1 divided by 36 savable throws. Thus, each throw is…
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