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Wednesday, April 21, 2004

Polls arg

Josh Marshall has a good post on why we shouldn't panic over the Gallup/CNN/USA Today and WaPo/ABC polls showing Bush ahead. Unfortunately his link sent me to polling report where there is a new Invesors Business daily Christian Science Monitor poll showing Bush ahead.

Following Marshall I look at polls all or in part in April. Summing 8 polls without Nader, Kerry cumulates 13 points ahead so averages 13/8 % ahead with a sampling standard error of very roughly 1%. Summing a partly overlapping set of 9 polls Bush is 5/9 % ahead with a sampling standard error of very roughly 1 % (well I said it was very roughly).

Ignoring the fact that I am doing this because I was struck by an apparent change (data snooping bias),
the lastest 3 (with Nader) give Bush ahead by an average of 5 % and the previous 6 gave Kerry ahead by an average of 5/3 %. The stardard error of the change due to sampling alone is very very roughly 2% which implies that Bush's gain would be strongly statistically significant.

I warn again about data snooping. I saw what appears to be a pattern and asked if it is statistically significant using techniques which would be valid if I had decided to apply them before looking at the data. Such an approach leads to size distortion (rejection of the null at the 5% level more than 5% of the time).

I ignore my warning above.

What can people be thinking ?

One argument is that anything that makes people focus on terrorism, foreign policy or war helps Bush even if they are focusing because of disasters due to Bush's decision to invade Iraq and discussion of Bush's non response to warnings in 2001. It could be the effect of Bush's $ 40 million add buy. One other possibility, which is supported in answers on who would deal with economic issues better in the WaPo/ABC poll, is that the ancient news about employment growth in March is influencing people. In particular, if emplyment is still growing OK people might be influenced by the fact that someone they know found a job even if the numbers haven't been tallied.

This is grim. It is only April. If I am already this obsessed, I will be completely crazy by November. I don't even want to think of the possbility of another recount.

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