Survey Basics

Pew Research Center uses benchmarking questions to ensure our surveys are accurate. Learn why and how we use these questions.

Given the wide range of people we speak to for our polls – and the issues we ask them about – it’s important to be as clear as possible about exactly who says what. In research circles, this practice is sometimes called “defining the universe."

Our latest Methods 101 video explores some of the ways these surveys differ from traditional probability-based polls.

Donald Trump's victory in 2016 and the U.K. "Brexit" decision rattled public confidence in polls. Our new video explains why well-designed polls can be trusted.

The second video in Pew Research Center's Methods 101 series helps explain question wording – a concept at the center of sound public opinion survey research – and why it’s important.

The U.S. has more foreign students enrolled in its colleges and universities than any other country in the world. Explore data about foreign students in the U.S. higher education system.

Read a Q&A with Michael Dimock, president of Pew Research Center, on recent developments in public opinion polling and what lies ahead.

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.

Opinion polls in the U.S. can address the same topic yet reach very different results. There are several reasons this can happen, but we tackle one of the most basic: Did the poll include or exclude the 45% who didn’t vote in November?

As oversampling and its possible effect on presidential polls are spotlighted ahead of Election Day, learn more about this practice and how pollsters adjust for it.