August 20, 2008 - pollster.com "Loopy" Zogby PollsBy David Moore
All pollsters, it seems, eventually find themselves with what Andy Kohut once referred to as "loopy" results. His comment was about the Gallup polls in the 2000 election, though in September 2004, Pew experienced such results itself, and of course several polls this campaign season have produced inexplicable or "wrong" numbers, as indicated by the subsequent primary election vote counts.
This time, it's Zogby's turn to confuse the masses. His latest Reuters/Zogby poll, based on a sample of 1,089 "likely voters" drawn from listed telephone numbers, conducted Aug. 14-16, 2008, shows McCain over Obama by 46% to 41%.
Two days earlier, Zogby reported substantially different results. His online poll (of self-selected people who want to be part of his Internet polling sample) of 3,339 "likely voters," conducted Aug. 12-14, showed Obama with a three-point lead, 43% to 40%.
By Zogby's own calculation of the margins of error of each poll, the difference between the two polls in McCain's support (46% in the later telephone poll vs. 40% in the earlier online poll) is statistically significant. The difference in Obama's support (41% vs. 43% respectively) would not be statistically significant. Still, the 8-point difference in the margin of McCain's lead would be significant - a McCain 5-point lead vs. an Obama 3-point lead in the earlier poll.
If we believe both polls, the period of Aug. 13-14 must have been a real bummer for Obama and an electoral high for McCain. Whatever it was that caused millions of voters to "change" their minds and gravitate toward the Republican candidate in the two-day period, however, escaped my notice. Perhaps others have been more observant.
Of course, there are reasons to discount both polls. Zogby has long been known for refusing to use sound methods in designing his samples. The use of only listed telephone numbers, and the self-selected samples of voters in his online surveys, are the two most salient problems. Still, his last pre-election polls often come close to the actual election results, and many news media outlets regularly publish his results.
Regardless of how loopy are Zogby's results, or his sampling methods, his polls contribute to what Kathy Frankovic, in her AAPOR presidential address in 1993, referred to as the "noise and clamor" of the polls. Thus, they're worth noting, if only in disbelief |
