Deltapoll Methodology


6th November 2019

The current Deltapoll political polling methodology is based upon an online quota sample approach, which, combined with a number of technical interventions seek a representative sample of GB adults aged 18+ (the eligible population).

Field process: set up and quotas
Deltapoll invites members of online panels to participate on each survey we undertake. Exclusions are applied to ensure that nobody can participate on consecutive polls, unless one or more non-standard conditions applies (such as the need to draw very large sample sizes). Quotas are applied to the following variables: gender, age, Government Office Region and 2017 vote.

Dealing with turnout
The underlying aim of a vote intention poll is transit from a representative sample of the eligible population to a representative sample of voters. In order to do so, it is first necessary to understand how likely it is that people will actually go and vote. We apply a standard 11-point scale of certainty, where 0 means that somebody is certain NOT to vote and 10 means they are absolutely certain to do so. Only those people who categorise themselves as 9-10/10 certain are included in the vote intention calculation.

Data are weighted to a number of geo-demographic and voter-graphic variables. Data are weighted to match demographic population targets from reliable sources (ONS population estimates, National Readership Survey, Labour Force Survey, etc). These weights are applied simultaneously by rim-weighting. Data are weighted by age within gender, social class, household tenure work status, Government Office Region, and educational attainment. Further sets of weights are applied for recall of 2017 General Election vote, recall of 2016 EU referendum vote, and political attention (10-point scale weighted to BES targets).

Data accuracy
Voting intention for the Brexit Party and UKIP is taken only from the constituencies in which they are standing. With the exception of a ‘final’ poll published on the day of an election, any vote intention poll is a snapshot of opinion at that moment in time, not a prediction of a future event. Further, all polls are subject to a wide range of potential sources of error. On the basis of the historical record of the polls at recent general elections, there is a 9 in 10 chance that the true value of a party’s support lies within 4 points of the estimates provided by an individual poll, and a 2 in 3 chance that they lie within 2 points. This is especially important to keep in mind when calculating party lead figures. We continually review our methods, and may make further adjustments or changes to any aspect of our polling methodology at any point in time. Any such change would be reported with the full tables on the Deltapoll website.

DeltapollAuthor: Deltapoll