Quote:
Originally Posted by Jack_O
I have one main concern with OPR. I only had time to briefly look over how it is calculated, but what I saw troubled me. One teams OPR is influenced by their alliance partners. This influence may not be very big, but it can add up. If a team goes to an event where the teams are generally "good", then their OPR will be higher. The opposite happens when the teams are generally bad. Most OPR stats are seperated by less than one point. As a result, one match with bad partners could screw everything up.
That is just my two cents. If I am wrong, or if I misunderstood something, please let me know.
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Welcome to ChiefDelphi!
You are in some respects correct, with some caveats and corrections. Yes, OPRs are based on calculations that involve the full alliance's score. However, "add up" is not the correct turn of phrase for potential inaccuracy--the more you play, specifically the more different alliances you (and your allies) play with, the less a role they should play in determining your OPR. As a simple example:
1114 + 000 + 999 = 150 ...this could mean that 1114 did nothing, and 000 scored 150 points alone
000 + 9999 + 8888 = 10 ...this makes it less likely that that happened
1114 + 7777 + 8888 = 180 ...again, it's getting clearer that 1114 has something going on here...
Imagine this continuing for another half dozen matches, and you'll see how more data tends to yield more accurate rather than less accurate results.
OPRs are also not as close as you think they are. For instance, at my last event, the standard deviation was 17.5, with a range of 69. Of 33 teams, the largest set within a 1pt range was 3 (13.7, 13.1, 13.0). Even at 60-some team events, the largest I found was 6. While they are somewhat sensitive, particularly at regionals with fewer qual matches, the amount that they'd change would probably be lower than the rating's useful precision anyway. And again, if your partners in that match are normally that bad in their matches, it certainly won't screw everything up for you.
EDIT: Or, you know, what Ed said. That too. (Except ever since EDIT: after 2011, 3 defensive robots can win matches.)