They will add roughly
However, from now through Election Day, we are making two adjustments to that process. First, due to potentially changes in the political environment, we will now base our targets upon survey interviews conducted over the preceding six weeks, rather than three months. Second, we will update the targets weekly, rather than monthly.
Makes some sense to me. The number of observations in the six week average is huge and party affiliation is not constant. However, I am not thrilled about suddenly changing the method.
The effect ?
For polling data released during the week of September 14-20, 2008, the new targets are 38.7% Democratic, 33.6% Republican, and 27.7% unaffiliated. For the first thirteen days of September, the targets were 39.7% Democrat, 32.1% Republican, and 28.2% unaffiliated. It should be noted that these figures indicate an improvement for Democrats since the beginning of the year.
So they just rejiggered their numbers 1.0 from Dem to Rep (about
Also they Kant spell.
"A one-percentage point decrease in the number of Democrats would half the same impact. "
update: and a similar 0.9 to 1% from Obama so a change in McCain-Obama of about 2% Robert you bozo.
This means that efforts to determine whether Obama has gained statistically significant ground on McCain recently have to add about 2% to Sunday and later released Rasmussen results to make them comparable to Saturday and before.
Unweighted average of the 4 most recent at realclearpolitics.com is Obama + 1 now corrected to Obama +1.5 (just for comparison with the past the new weights are probably better).
Older 4 + then values of trackers (data through 9/10) are (0+4+4+3-1+4+2)/7 = Obama - 2.3
Var of the avg of 4 = roughly (1/3000+1/3000+1/1000+1/1000)/16 = 1/6000
Of the older more like (2/3000+5/1000)/49 = about 1/9000 so sum of vars about
5/18000 so se around 1/60 so z-score 2.28 so the correction to the Rasmussen revision just pushes it over 2 (would be 1.98 without).
Boarderline significant evidence that Obama has gained on McCain.
Now weighting by sample size and using new Rasmussen weights implies exactly even (also if you include recent polls with Barr and Nader which average to zero Research 2000 Obama +3 ARG Obama -3).