Pairwise ranking: two at a time
Ranking a long list in one go is hard. Choosing between two is easy. Answer one quick question per pair and the ranking builds itself.
1Your list
Edit the list at any time and press Start again: answers for items that are still there are kept.
2Compare
Which matters more to you?
Keyboard: ← for the left item, → for the right, ↓ for about the same.
3Ranking
The ranking builds up here as you answer. Every item starts level.
Your list and answers are saved in this browser only.
How pairwise ranking works
Every item meets every other item exactly once. With n items that is n(n − 1) ÷ 2 pairs: 5 items take 10 choices, 10 items take 45 and 20 items 190. The pairs come in round-robin order, so the same item rarely appears twice in a row and you judge each pair fresh.
A win scores 1 point and "about the same" gives each item half a point. Items are ranked by points, the scoring used in round-robin tournaments and in Copeland's voting method. When two items finish level, the one that won their head-to-head goes first.
Sometimes the answers go round in a circle: A over B, B over C, yet C over A. That isn't a mistake on your part; it usually means those items are close, or that you were weighing them on different grounds. The tool counts these circles so you can look again at those items.
Sources
- Thurstone LL. A law of comparative judgment. Psychological Review 34 (1927), 273–286: the method of paired comparisons. Overview: Pairwise comparison.
- Copeland's method: ranking by pairwise wins, with half points for ties.
Questions
How many items can I rank?
Up to 20, which takes 190 comparisons. For longer lists, shortlist first, or use the decision matrix to score items against criteria.
Can I change an answer?
Undo steps back one answer at a time and asks that pair again. Reset answers starts over with the same list.
Why do items share a rank?
They won the same number of points and their head-to-head was a tie or part of a circle, so nothing separates them.