Saturday, September 8, 2012

Desperately seeking trends

Doug Schoen and Pat Caddell's latest piece of advice to Obama suggests that his campaign is in trouble and needs a sudden change. As evidence of Obama's recent troubles, they cherry-pick from a number of polls, noting that Obama is trailing Romney badly in the "battleground" state of Missouri (which isn't actually a battleground this year) and that Romney has closed the gap with Obama nationwide since May. Then they do this:
President Obama now leads by just one point in the latest PPP Florida poll (48%-47%)—down from a four-point lead (50%-46%) in an Aug. 22-26 CNN poll.
Look, I'm no pollster, but isn't comparing results across different polling firms and calling it a trend one of the cardinal sins of polling interpretation? And, given those polls' margins of error, aren't those two results statistically indistinguishable from one another?