Opinion polls are estimates of public opinion based on a sample of people, not a count of how everyone in the country intends to vote. A well-designed poll can be informative, but every poll has uncertainty and should be read in context.
What UKDecides shows for each poll
Where available, we show the polling organisation, fieldwork dates, sample size, published vote shares and a link to the original source. We do not treat a single poll as an election result or as proof of a trend.
Sampling and weighting
Pollsters recruit or contact a sample and then apply weighting so that the final sample better reflects the population they are trying to measure. Weighting variables and turnout assumptions vary by pollster, which is one reason two reputable polls conducted at similar times can differ.
Margin of error
Sampling error is only one source of uncertainty. A simple random sample of around 1,000 people is often associated with a margin of sampling error of roughly three percentage points for a percentage near 50%, but real political polling uses more complex designs and can also be affected by weighting, non-response, turnout modelling and question wording.
MRP
Multilevel regression and poststratification, usually shortened to MRP, combines survey responses with demographic and geographic information to estimate opinion in smaller areas such as constituencies. An MRP model is not the same thing as a conventional national voting-intention poll, and different models can produce different seat estimates.
Why polls disagree
Differences can arise from sampling, fieldwork dates, weighting, treatment of undecided voters, turnout models, question wording and methodological choices. The useful question is usually not which single poll is “right”, but what the broader body of evidence shows over time.