Here's a little analysis of a Time Magazine/Abt SRBI Poll
# 2008-4567: America by the Numbers, Oct. 3-6, 2008
*I used the available sampling weights
Obama / Biden 47.9%
McCain / Palin 42.7%
Other / Niether 02.0%
Undecided 07.5%
Undecided Voters
25.7 lean Obama
16.2 lean McCain
1.4 other
1.4 niether
55.4 still undecided
n=976
Let's assume that 25.7 of 7.5% of leaners, vote for Obama...you have:
.257 * 7.5 = 1.93% (allocated to Obama)
And add the McCain "leaners", you have:
.162 * 7.5 = 1.22% (allocated to Obama)
Thus, you now have:
47.9 + 1.93 = 49.8% Obama (95% Confidence Interval = 46.6% to 53% of popular vote
and
42.7 + 1.22 = 43.9% McCain
split the rest of the undecideds by 50%
and you get:
1 | 2
