Differing Polls

I usually leave comment on polls, and differences between them, to the end of month newsletter, but it may be useful to reflect on the difference between the One News/Colmar Brunton poll and the TV Three/TNS poll.

Both were published tonight, and the former had a 19% gap and the latter a smaller 10% gap. Both show National able to form a Government, but that is a significant 9% difference between them.

The first thing to note is that despite being both published today, they may be over different time periods. One News informs me that their poll was from Sat 12 April to Thursday 17 April. I have not been able to get hold of Three News yet, but generally in the past they have had a longer gap between end of polling and publication.

So one factor in their difference might be the days they polled over. The last week has had a lot happening, and it is quite likely this got reflected in polling done later in the week.

I understand there is likely to be a Fairfax poll out in the near future, so that may help provide some clarity once it is published.

UPDATE: TV Three tells me their dates were from 10 to 16 April, so not a huge difference in time periods.