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Median vs. mean consensus grades



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By MikeJ
Jun 26, 2012

Consensus grades on the site are currently calculated using the mean opinion. Switching to the median opinion would make the estimate more robust to outliers, and would prevent this sort of nonsense:

www.mountainproject.com/v/debbie-does-cpr/105921711

(Administrator decides he doesn't like a 5.11a climb so he gives it a 5.0 rating and screws up the consensus grade.)

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By Nick Wilder
Site Landlord
From The Bubble
Jun 26, 2012
climbing trip to Railay Beach, Thailand

I deleted the bogus ratings, and the route comments related to them.

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By agd
Jun 26, 2012
alaska

If the sample size is large enough and its normally distributed then the mean and median should be the same. With that said, I'm not sure what the sample size is...

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By Darren Mabe
From Flagstaff, AZ
Jun 26, 2012
Darren in the crux of Twist of Fate <br />Photo: Blake McCord

alexdavis wrote:
If the sample size is large enough and its normally distributed then the mean and median should be the same. With that said, I'm not sure what the sample size is...

beat me to it.
except there is nothing normal about the distribution on MP!

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By slim
Jun 26, 2012
tomato, tomotto, kill mike amato.

i agree that the median is the way to go.

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By agd
Jun 26, 2012
alaska

Young Gun wrote:
Switching to the median opinion would make the estimate more robust to outliers, and would prevent this sort of nonsense: www.mountainproject.com/v/debbie-does-cpr/105921711 (Administrator decides he doesn't like a 5.11a climb so he gives it a 5.0 rating and screws up the consensus grade.)


agreed.

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