The first video in Pew Research Center’s Methods 101 series helps explain random sampling – a concept that lies at the heart of all probability-based survey research – and why it’s important. Fresh ...

Researchers need to collect enough primary research to have a clear idea of the views and opinions of the people who are relevant to their research. The people relevant to the research are often ...

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 ...

When sampling a population, the numbers of organisms are counted within a sample site, and then the results multiplied to estimate the total number in the entire habitat. Large animals and plants can ...