Pew Research Center conducts public opinion surveys in the United States over the phone and, increasingly, online. But these two formats don’t always produce identical results. Respondents sometimes answer the same question differently depending on the format of the interview. This is known as a mode effect, and it’s a subject we’ve been studying for a few years now.

In our latest Methods 101 video, we look at mode effects in more detail and go over some of the ways in which survey answers can vary depending on whether respondents are talking to another person over the phone or filling out an online questionnaire by themselves.

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Watch our other Methods 101 videos:

How do you write survey questions that accurately measure public opinion?

What are nonprobability surveys?

How can a survey of 1,000 people tell you what the whole U.S. thinks?

How is polling done around the world?

What is machine learning, and how does it work?


Our previous Methods 101 videos explored the differences between nonprobability and probability-based surveys; the importance of question wording when designing surveys; and how a survey of 1,000 people can tell you what an entire country thinks. You can watch these videos or visit our methods page to learn more about the way we conduct our surveys.

You can also explore more about mode effects by reading some of our previous research:

Personal finance questions elicit slightly different answers in phone surveys than online

Few mode effects found when Americans are asked about their news consumption habits

Are Telephone Polls Understating Support for Trump?

From Telephone to the Web: The Challenge of Mode of Interview Effects in Public Opinion Polls

Courtney Kennedy  is Vice President of Methods and Innovation at Pew Research Center.