Sometimes a single poll diverges from the pack of results generated by everyone else. How can you tell when the pollster is doing a better job of picking up a new trend versus simply being wrong?
Peter Kellner offers an educative account of how these events occur, using as an example a poll that shows two political parties in a neck and neck race while everyone poll has one party ahead. It’s a UK example, but that doesn’t matter, the value of the essay is its discussion of how to weigh poll respondents who say they have no preference, how small samples affect conclusions and the like.
The article is worth reading both for its clarity and its modesty. Kellner’s own polling firm disagrees with the outlier poll, but he remains balanced and gentlemanly throughout his critique.