Pew Research CenterAugust 6, 2018

What are nonprobability surveys?

Many online surveys are conducted using “nonprobability” or “opt-in” samples, which are generally easier and cheaper to conduct. In our latest Methods 101 video, we explore some of the features of nonprobability surveys and how they differ from traditional probability-based polls.

MethodsAugust 6, 2018

Video Explainer: What are nonprobability surveys?

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

MethodsJanuary 26, 2018

For Weighting Online Opt-In Samples, What Matters Most?

A growing share of polling is conducted with online opt-in, or nonprobability, samples. This trend has raised some concern within the industry because, while low participation rates pose a challenge for all surveys, the online opt-in variety face additional hurdles.

MethodsAugust 1, 2016

Flashpoints in Polling

Many people wonder: Can polls be trusted? The following essay contains a big-picture review of the state of polling, organized around a number of key areas.

MethodsMay 2, 2016

What we learned about online nonprobability polls

The advantages of these online surveys are obvious – they are fast and relatively inexpensive, and the technology for them is pervasive. But are they accurate?

MethodsMay 2, 2016

Evaluating Online Nonprobability Surveys

Online nonprobability surveys are fast, cheap, and increasingly popular. We compared nine samples and found that accuracy varied substantially.