Why can opinion polls conducted by different pollsters on the same issue provide different results?
A9 There are several reasons why results amongst pollsters may differ – quite separate from the general issues relating to sampling error. Polls may have been conducted at a different time, even if they are published at the same time; in a run up to a general election people’s views fluctuate considerably as they hear different campaign manifestos, so a single day can make all the difference. Questions may be worded differently between pollsters, which in turn can affect the responses. In the same way, the ordering of questions can affect an outcome – respondents tend to ‘warm up’ to the interviewer as the survey progresses, so they may answer sensitive questions more honestly later in the interview. The method by which the poll is undertaken can also affect responses. The increasing popularity of internet polling has come about largely because some people may be happier to give their true opinions and feelings to a machine than to a person – and are choosing to respond to the survey r
