[EM] delta-p Approval strategy

[MIKE OSSIPOFF]

When I said that tie probabilities are more fundamental than delta-p,
I just meant that calculating the delta-p values depends on the 
probabilities of the revelevant ties & near-ties, whereas you don't
need the delta-p values to calculate estimate the tie probabilities.

Weber, at least in his _Journal of Economic Perspective_ article,
discussed only 2-way ties. That's probably because public elections
are the really imporant use of voting systems, and because of the
great simplification that results.

But, just as the delta-p approach could take n-way ties into account,
for committee voting, or could assume that all ties are 2-way, for
public voting, that's also true of Weber's method. Weber can take
into account n-way ties & near-ties.

So, let's not say that Weber's method is less accurate because, in
that article, it doesn't take into account n-way ties & near-ties.

A Corvair is more powerful than a Mustang--if we install a more powerful
motor in the Corvair than in the Mustang.

Weber can use the same inputs that you described for delta-p.

For public elections, where only 2-way ties are considered, can
the delta-p method match the great simplicity of Weber's method?

If delta-p is more complicated, more calculation-intensive, then
, more likely than not, it has more roundoff error than Weber would,
and is slightly (maybe not significantly) less accurate. I'm not saying
that delta-p isn't accurate enough, only that it's probably less accurate if 
it's considerably more calculation-intensive.

Until Weber & delta-p are completely worked-out for taking into account
n-way ties & near-ties, for small committees, I don't know which is
simpler. Of course the 2-way tie experience suggests that Weber will be
simpler, but we won't know about that till both methods are worked out
for small committees. So I'm not now claiming that Weber will be
simpler for small committees.

I don't want to seem too partisan about Approval strategy methods,
or Condorcet(wv) strategies. If I've seemed so, I'm not someone who'd
fight about those issues. I wanted to just state the case for
truncation in Condorcet(wv), and, in the case of the Approval strategy
methods, I objected to Richard's implication that delta-p is more accurate 
than Weber, because it's more accurate when we look at
n-way ties & near-ties with delta-p, but not with Weber.

Mike Ossipoff







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