21 October 2012

A Horse's Ass?

It would appear the Gallup is trotting down the same bridle path as The Literary Digest. While likely not as well known as the Chicago Tribune "Dewey Defeats Truman" headline, it is actually more significant today.
In retrospect, the polling techniques employed by the magazine were to blame. Although it had polled 10 million individuals (only about 2.4 million of these individuals responded, an astronomical sum for any survey), it had surveyed firstly its own readers, a group with disposable incomes well above the national average of the time (shown in part by their ability still to afford a magazine subscription during the depths of the Great Depression). The magazine also used two other readily available lists: that of registered automobile owners and that of telephone users. While such lists might come close to providing a statistically accurate cross-section of Americans today, this assumption was manifestly untrue in the 1930s. Both groups had incomes well above the national average of the day, which resulted in lists of voters far more likely to support Republicans than a truly typical voter of the time.

Today, Gallup is doing something similar, by relying on landlines. They say they've decreased the sampling using such, but when one poll is the outlier among many, it's wrong.

1 comment:

Euro2cent said...

That wikipedia bit was a good read. I'm surprised that it was a late as the 1930s that "modern scientific public opinion research" was kicked off.

The manufacture of consent by which you're ruled is a good deal older. Seems the non-scientific early approach worked pretty well. Except perhaps for the unpleasantness around the time of that Lincoln fellow.