With the latest One News poll Colmar Brunton revealed evidence of how much opinion – or the polled measure of opinion – can move over a short time.
One aspect that is usually ignored is that voters may think quite differently during an election campaign as they consider the governing possibilities and they decide how they want to vote – strategic voting has become more common – than how they might think in a spur of the moment poll mid-term.
The main poll question asked was “If a general election was held today, would you be eligible to vote?”
As usual One News show how the seats in Parliament would look if an election ‘was held today’.
But the polling in this week’s poll was done over 6 days, from Saturday 28 May to Thursday 2 June. And the poll was reported on Tuesday 7 June, 10 days after the first day of polling and 5 days after the last day day of polling.
How much could opinion change in that short a time? Quite a lot going by poll numbers split pre-MoU announcement and post-MoU announcement provided by Colmar Brunton:
The Memorandum of Understanding was announced by the Greens on Tuesday 31 May at 3.30 pm.
There is no indication of when people who were polled heard about the MoU, how much they heard about the MoU or whether they heard about the MoU at all before being polled.
There was quite a bit of ongoing discussion and news about the MoU after the polling was complete, especially over the following weekend with coverage of the Green AGM where Green leaders and Andrew Little spoke about the MoU.
And Labour and Green leaders, as well as Winston Peters, were interviewed about the MoU on Saturday on The Nation and on Sunday on Q+A.
So people who were polled in the last two and a half days of the polling period, as opposed to the first three and a half days days of the polling, would at best have only based their poll decisions on very preliminary consideration of the implications of the MoU, if at all.
It should also be noted that the MoU was not the only news over the polling period. Other news may have affected people’s opinions other than the MoU. Assuming that the MoU was the sole cause of a shift in opinion is baseless.
So as far as the MoU goes the before and after poll results should be viewed with a lot of caution.
As well as this single polls in general should be viewed with caution. Trends of one pollster over several months and aggregation of multiple pollsters are generally regarded as much better indicators of public opinion.
And another point – the before and after results show how much opinion measured by a poll can change in a short space of time, a matter of a few days.
NZ First support dropped from about 11% to about 7%, by about a third, a big variation.
Greens support increased by about a quarter, despite it being stated this wasn’t statistically significant I think it is notable.
And Labour support moved over 5%, from 26.1% to 31.3%. We don’t know whether support moved up a further 5% in the next 3 days, or dropped back again, or if the poll was an outlier poll.
All we know from this with any certainty is that polled opinion can change significantly over a short period of time.
Therefore the precise seating arrangements displayed by One News and others, and the ‘analysis’ of what a poll result might mean and why it might mean whatever they claim should be viewed with a lot of scepticism.
Reporting on polls by the mainstream media is usually awful and ignores the realities of political polling.
Single polls are no more than a rough indicator of opinion averaged over a few days.
One last point – a sample size of 1500 is unusual, 900-1000 is far more common.
As far as I understand it most polling results are usually obtained in the initial days of a polling period with the rest of the period used to fill the gaps in their demographic quotas.
So was a mid-poll decision made to increase the number of people being polled by 50%? Polling 628 people in two days seems unusual to me and may make polling variances more likely.
This latest Colmar Brunton poll demonstrates about how much opinion, or the measurement of opinion, can change over time, even over a very short time.