Here at Pew Research Center, we are often asked about how we conduct our research. We work hard to make our methodologies transparent and understandable, but we also know that survey mode effects and ...

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 ...

Imagine you're tasked with sending a team of football players onto a field to assess the condition of the grass (a likely task for them, of course). If you pick their positions randomly, they might ...

When doing inventory for cryptic and rare species, it can be difficult to determine with great confidence that a sampled area has no occurrences of the target species. Boreal Felt lichen (Erioderma ...