PDGA rating ?

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PDGA rating ?

Postby MR. WICK » Thu Jul 24, 2008 7:49 am

Do lower rated rounds (rounds that are well off your avearage) get thrown out?
The reason I ask is my rating at the last update was 934. I won the next tournament in advanced with ratings of 975 and 951. I followed that up by battling for DFL in the next tourney shooting rounds rated at 831 and 882.
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Postby Timko » Thu Jul 24, 2008 7:58 am

I think if they're 2.5 Standard Deviations from your average. Chuck should know this.

So the 831 round may get thrown out. Doubtful for the 882.
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Postby Chuck Kennedy » Thu Jul 24, 2008 8:14 am

Rounds more than 2.5 standard deviations below your average rating are thrown out or more than 100 points below your rating, whichever is smaller. For example, if your SD is 44 then 2.5 times that is 110 which is more than 100 pts. So in that case, rounds more than 100 pts below you rating would be tossed. If your SD is 30 then 2.5 times that is 75 which is common for better players above say 930 rating. For them, any rounds more than 75 points below their rating are tossed. For the average PDGA member, roughly 1 in 50 rounds get tossed (2%).
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Postby curt » Thu Jul 24, 2008 8:26 am

If you're curious about your standard deviation this will help: http://invsee.asu.edu/srinivas/stdev.html

once you get you standard deviation, multiply by 2.5 and then subtract that number from your rating. That should get you close. (i say close because it seems no matter how careful I am, my math always ends up at least a little different than the pdga's (most likely carelessness or incomplete understanding of the formula on my part))
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Postby some call me...tim? » Thu Jul 24, 2008 8:43 am

ugh...just went through all my old scores, that wasn't the best trip down memory lane. standard deviation of about 25 points, so if i play any rounds 63 pts below my rating, they should be wiped out.
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Postby Chuck Kennedy » Thu Jul 24, 2008 8:46 am

We have made one recent change in favor of the player. The SD is now calculated without your lowest rated round included in the calc. This excludes your worst round from the SD making it a little more likely it will be dropped if it's quite a bit lower than your other round ratings.
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Postby curt » Thu Jul 24, 2008 8:59 am

I have one other question about the calculations. I know the most recent 25% of rounds count double for the rating. Do they count double for the standard deviation. If not, do you use the rating calculated with or without them counting double to subtract the standard deviation from.

I'm not sure this makes sense , so i'm going to try to include an example:

let's say i shoot the following 4 rounds in this order: 900, 900, 900, 1000

900+900+900+1000=3700
std=43.3
rating=925

900+900+900+900+1000+1000=4700
std=48.9
rating=940

would the appropriate std be 43.3 or 48.9.
Also would you subtract std*2.5 from 925 or 940
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Postby Chuck Kennedy » Thu Jul 24, 2008 9:07 am

The SD is calculated from your group of round ratings before weighting. The double weighting is determined after the rounds are dropped if any.
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Postby curt » Thu Jul 24, 2008 9:17 am

thanks
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Postby MR. WICK » Thu Jul 24, 2008 9:19 am

ugghhghg math.
Thanks for the replies. That helps.
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Postby Steady 26542 » Thu Jul 24, 2008 11:48 am

Chuck Kennedy wrote:We have made one recent change in favor of the player. The SD is now calculated without your lowest rated round included in the calc. This excludes your worst round from the SD making it a little more likely it will be dropped if it's quite a bit lower than your other round ratings.


So, the lowest rated round in the past 12 months gets tossed for the purpose of calculating the SD. Then, any round outside of -2.5 SD gets tossed from being used in one's rating. Correct?

Throwing out the lowest rated round should tighten up the SD, which in turn will get more scores tossed, which should, in effect, raise player ratings. Whew...

(I'll have to change my spreadsheet formula... Damn)
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Postby Leopard » Thu Jul 24, 2008 11:57 am

Chuck -- HOW DO YOU DO IT???

I'm interested in how the ratings are maintained... is it just a massive spreadsheet (or grouped series) or did you write some software for it? And how do you add results? I could ask speculative questions but I'm dumb about this. Everyone would have a rating of "hello world" if it were up to me.

So what the hell? It's magic and I can't stand magic.
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Postby stoneman » Thu Jul 24, 2008 12:51 pm

"Hello World" IS my rating. :D
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Postby Chuck Kennedy » Thu Jul 24, 2008 1:11 pm

Throwing out the lowest rated round should tighten up the SD, which in turn will get more scores tossed, which should, in effect, raise player ratings. Whew...

There's a slight inflation factor due to this change but almost imperceptable numerically. Remember that the bottom rated round excluded from the SD calc is only excluded from the final ratings calc if it still falls outside the 2.5SD/100 pt criteria. That happens for only about 1 in 50 players.

As far as doing the calcs for the PDGA, Roger Smith who lives near Joliet, IL and doesn't play PDGA events hardly at all is my partner that handles most of the data processing dirty work in MS Access. First, TD send their reports to PDGA HQ. They enter those into the PDGA database. Then they export a massive file to Roger. He does his thing using Access.

I'm the one who looks at each TD report and sets the course configurations each division plays semi-automatically into an Access file Roger provides for me that includes all of the new events to be processed for this ratings update. This is a key step that makes it unlikely we can just have ratings updates live online. There are too many errors and omissions in the TD report that need to be tracked down and corrected. I send that file back to him and he merges it with the overall database that goes back to 1998 when we started and processes the new ratings.

That file gets sent to Dave Gentry at PDGA HQ when ready. It's reviewed for errors offline using some test reports Roger produces that indicate potential problem ratings that fall outside some control boundaries such as a 10 yr old girl shooting a 1020 round. Once reviewed, then Dave uploads it into the live PDGA database and you see the new numbers.
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Postby discdawg » Thu Jul 24, 2008 2:31 pm

How do you get a rating number? Do you have to play a PDGA tournament?

How are the numbers calculated? Based off of the course?
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