Abromowitz speaks: No poll tightening - Democratic Underground

grantcart

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Thu Oct-23-08 12:03 PM
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Abromowitz speaks: No poll tightening

http://www.pollster.com/blogs/abramowitz_tracking_the_tracki.php

for background Dr. Abromowitz is considered the dean of polling. Here is what phrigndumass says of him;

Yes, I've been googling about him lately. Abramowitz considers EVERYTHING! And he projected Obama winning with 54% back on September 11, when the numbers didn't look as good for us as they do now.

His calculus produces a trend line that's beyond my ability to comprehend, something similar to a poly-20 using historic sub-formulas. For comparison, Excel spreadsheets allow up to a poly-6, because anything more than that would cause Excel to crash when you open the file, lol

In evaluating the national polls Abromowitz had this to say;

There is no evidence in these data of any tightening of the presidential race over this time period.
Figure 1 shows the trend in Obama's average lead in six tracking polls that provided results every day between October 12 and October 20 (the Battleground Poll does not report results on the weekend). While Obama's lead increased in some polls and decreased in others during this period, the results in Figure 1 show that the overall average changed very little. Obama led by an average of 6.5 points on October 12thand he led by an average of 7.0 points on October 20st, the final date included in this analysis.

If there is no overall trend, then what explains the day to day movement in the tracking polls? One possibility is that most if not all of the day to day movement was due to sampling variation-that it was nothing more than random noise. In order to test this hypothesis, I calculated the correlations among the day-to-day results of the seven tracking polls over these ten days. The correlations between individual pairs of polls varied considerably. Some were strongly positive, some were very weak, and some were strongly negative. Nothing much should be made of this, however, because of the very limited number of days on which these correlations were based. What is significant, however, is that the average correlation among the seven tracking polls over this ten day period was -.06. This means that there was basically no relationship in the day-to-day movement of these polls during this time period. Whether Obama's support was going up or down in one poll was unrelated to whether his support was going up or down in the other six polls.

The lesson that should be drawn from these findings is not that there is any fundamental flaw in the tracking polls. Random variation is unavoidable in public opinion polling. What these findings do indicate, however, is that poll-watchers should not pay too much attention to the day to day movements in these polls unless they see all or most of them moving consistently in one direction over a period of time. Similarly, polling organizations should avoid overemphasizing the significance of the day to day movements in their own polls and pay more attention to whether their results are consistent with those of other polls.