ComRes is a member of the British Polling Council (BPC) and abides by its rules.

 

We agree with the BPC’s principal objective which is to “ensure standards of disclosure designed to provide consumers of survey results that enter the public domain with an adequate basis for judging the reliability and validity of the results”.

 

The information below is supplied to meet this objective.

Interview method - telephone
Population effectively sampled - all adults aged 18+

 

Sampling Method

Within each government office region a random sample of telephone numbers is drawn from the entire BT database of domestic telephone numbers. Each number so selected has its last digit randomised to provide a sample including both listed and unlisted numbers.

 

Data weighting

Data are weighted to the profile of all adults aged 18+ (including non telephone owning households). Data are weighted by sex, age, social class, household tenure, work status, number of cars in the household and whether or not respondent has taken a foreign holiday in the last 3 years.

Targets for the weighted data are derived from the National Readership survey, a random probability survey comprising 34,000 random face-to-face interviews conducted annually.

ComRes also applies two further weights to political polls.  First, we weight by past vote recall to ensure a politically representative sample, comparing the actual result of the 2005 General Election with an average of the past four months’ past vote recall (to address possible volatility).

Second, we weight polls according to the likelihood of respondents to actually vote. We do this by offering a scale from 1 to 10 where 1=certain not to vote and 10=absolutely certain to vote. If respondents answer 4 or below we assume they are unlikely to vote and exclude them from the voting intention calculation. Those who answer between 5 and 10 are then asked which party they would vote for and their answers are weighted from 0.5 to 1.0 respectively. If respondents decline to offer a choice of party they are asked how they would probably vote if it were a legal requirement to do so.

 

All who remain undecided or refuse to say for whom they would vote are then allocated a party, weighted by likelihood to vote (from 0.5 to 1.0 as appropriate), according to which party they most closely identify with.

In summary, the percentage support shown for each party is weighted to past vote recall, based on strength of likelihood to vote, excluding those who decline to state how they would vote and which party they most closely identify with.
The BPC website is at www.britishpollingcouncil.org