Start here · Essential guide
How Opinion Polls Work and Why They Differ
A plain overview of how opinion polls are designed, from choosing a sample to weighting answers, and why two careful polls can still report different pictures.
Evidence and Method
Public Opinion and Polling
How opinion is measured and why polls disagree.
Margin of Error in Plain Language
What a poll's margin of error does and does not tell you: sampling uncertainty explained without formulas, plus how to read gaps, subgroups and close races.
Non-Response and the People Who Never Answer
Why the people who decline or never reach a survey matter, how non-response bias can tilt results in a particular direction, and what pollsters try to do about it.
Online Opt-In Polls Versus Probability Samples
How self-selected online polls differ from randomly drawn probability samples, what each kind of survey can support, and how to judge a result by its source.
Social Desirability and Honest Answers
Why survey respondents sometimes shade answers toward what seems acceptable, which topics are most affected, and how researchers try to reduce the effect.
Tracking Surveys and How Repeated Questions Show Change
Why asking the same question the same way over time is the most trusted way to see opinion shift, and what can break a trend line such as wording or method changes.
Weighting and Adjusting Survey Results
How raw survey responses are adjusted to match a population, what weighting can and cannot fix, and the ways adjustments can go wrong or add uncertainty.
Why Attitudes on Values Tend to Move Slowly
How opinions on deep values often change through generations replacing each other more than through individual conversion, and what that means for reading survey trends.
Related topics
More in evidence and method
How Trend Data Is Collected Where the numbers behind trend stories come from and what each source misses. Correlation, Causes and Competing Explanations Reasoning tools for judging why a trend happened. Fads, Hype and Trend Lifecycles How trends rise, spread and fade, and how attention distorts the picture.