# [EM] Cloneproof SSD

Blake Cretney bcretney at postmark.net
Mon Jan 22 16:46:37 PST 2001

```"LAYTON Craig" <Craig.LAYTON at add.nsw.gov.au>, on the subject of 'RE:
[EM] Cloneproof SSD', is quoted as:
>>It isn't clear to me how you use random ballot to decide which
>>pairwise defeat you drop.
>>
>>Example: Suppose that you have to decide whether W:X or Y:Z is
dropped.
>>Suppose that the randomly chosen ballot is W > Y > X > Z. How does
this
>>randomly chosen ballot helps you to decide which pairwise defeat
should
>>be dropped?
>
>There would be a few ways. You could always say that the pairwise
contest
>expressed first (ie, the one in which the lowest numbered candidate of
the
>pair is the highest).  In the above case it would be W:X.  Although,
it
>would probably make more sense to do the opposite (the pairwise contest
in
>which the lowest numbered candidate of the pair is the lowest).

Tideman suggests you should rank the pairwise contests by the pairwise
winners .  So, if you have W>X and Y>Z, and a tiebreaker of W>Y>X>Z, the
pairwise contests (or "pairs" as Tideman calls them) are ordered W>X and
then Y>Z, since W>Y in the tiebreaker.  If you have pairwise ties, then
they are processed as victories for the candidate higher in the
tie-breaker, in order of place in the tiebreaker.  Victories of the same
candidate can be processed in arbitrary order, since this does not
affect the result.

I'm referring to
Zavist TM, Tideman TN (1989) Complete Independence of Clones in the
Ranked Pairs Rule. Social Choice and Welfare 6:167-173.

My Ranked Pairs page is at:
http://www.fortunecity.com/meltingpot/harrow/124/path

---
Blake Cretney

```