Cardinal-weighted pairwise comparison: Difference between revisions
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== Cardinal-weighted pairwise == |
== Cardinal-weighted pairwise == |
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{{Distinguish|rated pairwise preference ballot}} |
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"'''Cardinal pairwise'''" and "'''CWP'''" are shorter names for "cardinal-weighted pairwise comparison", a method first proposed by James Green-Armytage in June of 2004. |
"'''Cardinal pairwise'''" and "'''CWP'''" are shorter names for "cardinal-weighted pairwise comparison", a method first proposed by James Green-Armytage in June of 2004. |
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===Ballot types=== |
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1. One way to ballot for CWP is to have a separate ordinal and cardinal ballot, and to require that if a voter gives candidate R a higher rating than candidate S, then that voter must also give candidate R a higher ranking than candidate S. |
1. One way to ballot for CWP is to have a separate ordinal and cardinal ballot, and to require that if a voter gives candidate R a higher rating than candidate S, then that voter must also give candidate R a higher ranking than candidate S. |
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2. A simpler way to ballot for CWP is to use only a cardinal ballot, and to derive the ordinal information from the cardinal information. The only disadvantage of this is that it creates an additional [[tactical voting|compromising-compression]] incentive not found in the first version. However, this additional incentive should be extremely minor if the scale is sufficiently fine. |
2. A simpler way to ballot for CWP is to use only a cardinal ballot, and to derive the ordinal information from the cardinal information. The only disadvantage of this is that it creates an additional [[tactical voting|compromising-compression]] incentive not found in the first version. However, this additional incentive should be extremely minor if the scale is sufficiently fine. |
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For example, assume that the scale consists of integers from 0 to 100. If my sincere preferences are J>K>L, and I want to make the J>K defeat as weak as possible while making the K>L defeat as strong as possible, I can vote J:100, K:99, L:0. There is only a very small temptation to vote J: 100, K:100, L:0. This temptation can be reduced even further by allowing decimal ratings, e.g. J:100, K:99.99, L:0. |
For example, assume that the scale consists of integers from 0 to 100. If my sincere preferences are J>K>L, and I want to make the J>K defeat as weak as possible while making the K>L defeat as strong as possible, I can vote J:100, K:99, L:0. There is only a very small temptation to vote J: 100, K:100, L:0. This temptation can be reduced even further by allowing decimal ratings, e.g. J:100, K:99.99, L:0. It can be mostly eliminated by allowing voters to use an [[approval threshold]] to indicate their cardinal support. |
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==Approval-weighted pairwise== |
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"'''Approval weighted pairwise'''", "'''AWP'''", or "'''approval pairwise'''" is the special case of cardinal pairwise in which the only available ratings are 0 and 1. AWP can use a ranked ballot with an approval cutoff. |
"'''Approval weighted pairwise'''", "'''AWP'''", or "'''approval pairwise'''" is the special case of cardinal pairwise in which the only available ratings are 0 and 1. AWP can use a ranked ballot with an approval cutoff. |
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== Example == |
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10 A:10 B:2 |
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9 B:10 A:0 |
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A [[Pairwise beat]]<nowiki/>s B 10 voters to 9, and has a rating differential of 80 points (equivalent to 8 votes on a scale of 0 to 10) against B. |
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==External resources== |
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*[http://www.mcdougall.org.uk/VM/ISSUE19/I19P2.PDF Cardinal pairwise paper], as published by [http://www.mcdougall.org.uk/VM/INDEX.HTM Voting Matters]. |
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* |
*[http://lists.electorama.com/pipermail/election-methods-electorama.com/2004-June/013280.html Initial proposal] on election methods list. |
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[[Category:Single-winner voting methods]] |
[[Category:Single-winner voting methods]] |
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