Phone vs. online surveys: Why do respondents’ answers sometimes differ? | Pew Research Center

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.
http://www.pewresearch.org/fact-tank/2019/02/07/phone-vs-online-surveys-why-do-respondents-answers-sometimes-differ-by-mode/