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Topic: Is there a way to calculate an average ranking from uneven lists?
Replies: 12   Last Post: Nov 2, 2013 12:55 PM

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 Virgil Posts: 8,833 Registered: 1/6/11
Re: Is there a way to calculate an average ranking from uneven lists?
Posted: Oct 27, 2013 3:36 PM

In article <chpq69prq63kh364qqmphkmqedhgm5ti6h@4ax.com>,
Jennifer Murphy <JenMurphy@jm.invalid> wrote:

> There are many lists containing rankings of great books. Some are
> limited to a particular genre (historical novels, biographies, science
> fiction). Others are more general. Some are fairly short (50-100 books).
> Others are much longer (1,001 books).
>
> Is there a way to "average" the data from as many of these lists as
> possible to get some sort of composite ranking of all of the books that
> appear in any of the lists?
>
> I took a crack at it with a spreadsheet, but ran into problems. I will
> explain it briefly here.
>
> If the lists are all the same length and include exactly the the same
> books, the solution is relatively simple (I think). I can just average
> the ranks. I can even add a weighting factor to each list to adjust the
> influence on the composite ranking up or down.
>
> I ran into problems when the lists are of different lengths and contain
> different books. I could not think of a way to calculate a composite
> ranking (or rating) when the lists do not all contain the same books.
>
> Another complicationb is that at least one of the lists is unranked (The
> Time 100). Is there any way to make use of that list?
>
> I created a PDF document with some tables illustrating what I have
> tried. Here's the link to the DropBox folder:
>
> https://www.dropbox.com/sh/yrckul6tsrbp23p/zNHXxSdeOH

One way to compare rankings when there are different numbers of objects
ranked in different rankings is to scale them all over the same range,
such as from 0% to 100%.

Thus in all rankings a lowest rank would rank 0% and the highest 100%,
and the middle one, if there were one, would rank 50%.
Four items with no ties would rank 0%, 33 1/3%, 66 2/3% and 100%,
and so on.

For something of rank r out of n ranks use (r-1)/(n-1) times 100%.
--

Date Subject Author
10/27/13 Jennifer Murphy
10/27/13 Virgil
10/27/13 Jennifer Murphy
10/27/13 Virgil
10/28/13 Jennifer Murphy
10/28/13 Virgil
10/28/13 David Bernier
10/28/13 Graham Cooper
10/29/13 Jennifer Murphy
10/29/13 Graham Cooper
10/29/13 David Bernier
10/29/13 David Bernier
11/2/13 Jennifer Murphy