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I prophesy disaster View Drop Down
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    Posted: May 04 2018 at 06:56

I was having a look at the top Symphonic Prog albums for the years 1980-2018 and I saw that Hybris (Änglagård) is at #1 with a rating of 4.38 (1578 ratings) and QWR = 4.3308, and From Silence To Somewhere (Wobbler) is at #2 with a rating of 4.48 (318 ratings) and QWR = 4.2719. By contrast, according the top albums overall, Silence To Somewhere (Wobbler) is at #18 with a rating of 4.48 (318 ratings) and QWR = 4.3689, and Hybris (Änglagård) is at #20 with a rating of 4.38 (1578 ratings) and QWR = 4.3536. Note that the QWR and hence the rank order differs between the different choice of filters.

 


 
No, I know how to behave in the restaurant now, I don't tear at the meat with my hands. If I've become a man of the world somehow, that's not necessarily to say I'm a worldly man.
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someone_else View Drop Down
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Points: 24316 		Post Options Post Options   Thanks (0) Thanks(0)   Quote someone_else Quote  Post ReplyReply Direct Link To This Post Posted: May 04 2018 at 07:54
There is a difference between QWR-determined rankings depending on the choice of the filters. Above all queries, on top of the page it says:
  • Rank of an album: We use a calculation that compare an album average rating and number of ratings over all others albums in the query using this theory (http://en.wikipedia.org/wiki/Weighted_average)
    • to create a variable every query "QWR" (AKA: Query Weighted Rating) use for ordering.
The QWR is calculated from the result of the query and therefore it may differ with every modification on a query filter. The average ratings and numbers of ratings of each queried album interact with each other. Thus the ratings are relative, not  absolute. That's why I always enter a minimum number of ratings and an average rating value other than 0: if either of these fields has a value of 0, the results are unpredictable.
Yikes.

Years ago, the MikeEnRegalia-algorithm was used to calculate the ranking of an album. This was an absolute ranking, based on the number of ratings to the power of three multiplied by the average rating to the power of two or the other way around, if I remember it right.

It's not a bug, it's a feature.



Edited by someone_else - May 04 2018 at 07:56
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I prophesy disaster View Drop Down
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Points: 4811 		Post Options Post Options   Thanks (0) Thanks(0)   Quote I prophesy disaster Quote  Post ReplyReply Direct Link To This Post Posted: May 04 2018 at 09:04
Originally posted by someone_else someone_else wrote:

The QWR is calculated from the result of the query and therefore it may differ with every modification on a query filter.
 
Hmmm. I thought I understood how the QWR was calculated, but if the value depends on all the other albums returned by the query, then it would seem that I'm mistaken. But I still don't see how the QWR depends on anything but the ratings and reviews of the album itself.
 
 
 
No, I know how to behave in the restaurant now, I don't tear at the meat with my hands. If I've become a man of the world somehow, that's not necessarily to say I'm a worldly man.
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someone_else View Drop Down
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Points: 24316 		Post Options Post Options   Thanks (0) Thanks(0)   Quote someone_else Quote  Post ReplyReply Direct Link To This Post Posted: May 05 2018 at 04:44
Look at this query: Prog Folk, 2018, 2 to 3 ratings, min. avg. = 1

Then look at this: Prog Folk + RIO/Avant, 2 to 3 ratings, min. avg. = 1 and see what happens with the QWR.

Note: When I change the parameters for Prog Folk alone (to 1 rating or more or whatever), the QWR's don't change.
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