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). The weighting is undertaken 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 weighting 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 its political polls.  First, we weight polls according to the reported likelihood that respondents will vote. That likelihood is obtained by offering respondents 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 no effort is made to ascertain their voting intentions. Those who answer between 5 and 10 are asked which party they would vote for and their answers are weighted from 0.5 to 1.0 in accordance with their reported likelihood of voting.

 

Secondly, to ensure the sample is politically representative, we weight by how respondents recall having voted at the last general election. This weighting is based in part on comparing the distribution of this recall vote (for those who declare for whom they voted) with the actual result of the 2005 General Election and in part with the average past vote obtained in our previous twelve polls. Three-quarters of the weight is based on the former comparison and one-quarter on the latter. This procedure is designed to correct for any sampling bias and sampling error (respectively), while acknowledging the existence of response error in the reporting of past vote.
 
If respondents decline to name a party in response to the voting intention question, they are asked how they would probably vote if it were a legal requirement to do so and allocated this party.  All who continue to remain undecided or refuse to say for whom they would vote are then allocated a party, according to the party with which they most closely identify. In both cases, the data are weighted by reported likelihood of voting.
 
The BPC website is at www.britishpollingcouncil.org