Polling techniques may account for erratic predictions in Virginia

[mahatmakanejeeves]

Retweeted by Dave Weigel: https://twitter.com/daveweigel

In a shift, most of the public #VAGOV polls have been conducted using voter lists. The RDD polls are the outliers.

Link to tweet

Polling techniques may account for erratic predictions in Virginia

Depending on the survey, the governor's race is either a dead heat or shoo-in — for either candidate.

By STEVEN SHEPARD 10/31/2017 08:47 PM EDT Updated 10/31/2017 10:10 PM EDT

At first blush, polling in Virginia’s closely watched race for governor looks all over the map, from a 17-point lead for Democrat Ralph Northam to an 8-point advantage for Republican Ed Gillespie.

But what might appear to be a breakdown in pollster reliability may have a much simpler explanation: Not all surveys are conducted the same way, with variations in how questions are asked accounting for the large range of possible results in Virginia.

For decades, pollsters randomly dialed phone numbers to achieve probability sampling: the principle that every person has an equal chance of being selected to participate in the survey. As state election authorities and political parties became more sophisticated, however, campaign polling consultants began to call only those on the voter rolls — and, later, only those voters who regularly participated in elections.

In recent years, more public pollsters have embraced this private technique. Now, with a week until Virginians go to the polls — and with pollsters eager to rebuild their standing after mistaken predictions in the presidential election last year — the majority of public surveys in the governor's race are conducted this way. The public polling conducted using lists of registered voters, a method that proponents say is much more consistent, suggests Northam is the slight favorite.

[nycbos]

1. I didn't buy the poll that showed Northam up by 17, or the poll...

... that showed Gillespie leading by 8.