[EM] XA

[Andy Jennings]

On Mon, Oct 31, 2016 at 7:13 PM, Michael Ossipoff <email9648742 at gmail.com>
wrote:

> What makes XA do that more effectively than MJ? What's the main advantage
> that distinguishes how XA does that from how MJ does it, or the results,
> from the voters' strategic standpoint?


Michael,

As Rob said, the median is not terribly robust if the distribution of votes
is two-peaked:
http://www.rangevoting.org/MedianVrange.html#twopeak
And I'm afraid many of our contentious political elections are two-peaked,
at least in the current environment.

With MJ, I like the fact that if the medians for all candidates will fall
between B and D, then I can use the range outside that for honest
expression.  Yet in the back of my head, I know that if everyone tries to
"use the range outside that for honest expression", then the medians won't
be in that range anymore and it seems like a slippery slope to everyone
using only the two extreme grades.

XA solves this problem by making the more extreme grades more difficult to
achieve.  As Rob said, in the case where everyone grades at the extremes,
the XA will match the mean.

On the other hand, I admit that:
1) with the median, 50% would have to give the top grade for a candidate to
receive that grade.  And 50% would have to give the bottom grade for a
candidate to receive that grade.  I consider both of these very unlikely.
2) MJ is not just "the median", it has a tie-breaking scheme which
mitigates this somewhat.

~ Andy
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