Serious polling requires careful data collection and careful adjustment. It doesn't mean much to say your poll is a "probability sample" when your nonresponse rate is 90 percent.

Pew Research Center designed this study to assess the current state of online survey sampling methods – both probability-based and opt-in – and determine their accuracy on general population estimates ...

Consider a population of 70 individuals, for which you wish to estimate the mean annual income, μ. Assume that you have decided to use the following estimation procedure to make your estimate: simple ...

Detailed information on Pew Research Center international survey meethodology, such as mode of interview, sampling design, margin of error, and design effect, for each country we survey, organized by ...