Reply #48: can you justify your formula for alpha?

[OnTheOtherHand]

Kerry Responders = Kerry vote% * Alpha * Total Responders

from which you correctly algebraically derive

Alpha = K/B = Kerry Responders /(Kerry Vote% * Total
Responders)

(K is the Kerry response rate, and B is the Bush response rate)

But why should it be true that
Kerry Responders =(?) Kerry vote% * (K/B) * Total Responders??

I think you were thinking something like

Kerry Responders = Kerry vote% * (K/R) * Total Responders

where R would be the overall response rate. So, for instance, suppose we have 100 Bush voters and 100 Kerry voters, but K = 56% and B = 50%, so we end up with 56 Kerry responders and 50 Bush responders (106 total responders). Alpha = 0.56/0.50 = 1.12. By your equation, it should be true that

56 =(?) 0.50 * 1.12 * 106

but actually the right side of that equals 59.36.

If you do

56 == 0.50 * (0.56 / 0.53) * 106

it works.

K/B is close to K/R when B is close to R regardless of K because there are very few Kerry voters, as in the high-Bush precincts -- or when K and B are close to each other, as they apparently were in the high-Kerry precincts. So when I eyeballed those alphas, they seemed familiar. It's the one in the middle that really seems too low to generate a WPE of -8.5%. Ron Baiman figured it at 1.186.