A poll of 47

The Herald each election does a Mood of the Nation survey when they get reporters onto the street and interview around 500 people. I think this generally is a good initiative. They report that it is unscientific, but it allows them to use actual quotes from people to use in their stories. So long as they stress the survey is unscientific, and the focus is more on what people said rather than the numerical results, I think that is fine.

But you can take these street surveys too far. Off memory, in 2008 a street survey of 100 people was reported by the Herald with great prominence as showing Judith Tizard retaining her seat. She lost of course.

This time we have a street survey of just 47 people in Epsom, that generates a story. It says:

John Banks has some support in the wealthy suburb of Remuera, but is less popular on the liberal fringes of the Epsom electorate, according to a Herald street survey.

A poll of 47 Epsom voters yesterday found the National candidate ahead of Act’s Mr Banks by 22 votes to 20.

It is ridiculous to do a story on a street poll of 47. First of all, you have the sampling problem – that in fact it is a poll of people who happened to be out on a street – in no way random.

But even if you overlook the fact it is a street poll, the sample size is ridiculously low.  The margin of error is 14.7%!

I generally regard 300 as the minimum acceptable for an electorate poll. That gives a 5.8% margin of error. A sample of 47 is close to useless.