Adam Hayes, Ph.D., CFA, is a financial writer with 15+ years Wall Street experience as a derivatives trader. Besides his extensive derivative trading expertise, Adam is an expert in economics and ...

Early survey statisticians faced a puzzling choice between randomized sampling and purposive selection but, by the early 1950s, Neyman's design-based or randomization approach had become generally ...

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 ...

Ali Hussain has a background that consists of a career in finance with large financial institutions and in journalism covering business. Vikki Velasquez is a researcher and writer who has managed, ...

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 ...

Probability sampling has enjoyed a privileged position for good survey practice since the beginning of last century. Jerzy Neyman (1934) decisively contributed to this situation with his theory for ...

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 ...