With more people dropping land-line phones and an increasing reluctance to participate in telephone polls, online surveys are becoming more popular. There’s a question, however, of how accurate they are.

Participants in online polls are largely self-selecting, which takes away the quality of randomness that was supposed to be the key to accuracy in telephone polls. Pollsters ranging from the traditional—such as Reuters/Ipsos—to newcomers such as SurveyMonkey all must bake in more statistical modeling to account for the difference.

Pew Research Center conducted—of course!—a survey last year to discover what differences appear between telephone polls and those conducted online. Pew found that questions asked on the phone about the quality of a respondent’s life tended to have more positive answers than those posed online. Societal discrimination was another area that had a noticeable difference, with telephone subjects more often saying gays and lesbians, Hispanics and blacks face a lot of discrimination.

One beneficiary of online polling appears to be Republican presidential contender Donald Trump. He consistently does better in online surveys than he does in those conducted over the phone, according to The New York Times. “Plenty of research suggests that the social acceptability of an opinion shapes the willingness of poll respondents to divulge it, and it’s imaginable that voters would be reluctant to acknowledge support for a controversial figure like Mr. Trump,” Nate Cohn wrote at the Times.

-Steve Straehley

To Learn More:

Online Polls Are Rising. So Are Concerns About Their Results. (by Nate Cohn, New York Times)

From Telephone to the Web: The Challenge of Mode of Interview Effects in Public Opinion Polls (Pew Research Center)

Gallup Lawsuit Settlement Could Benefit Republicans in Future Opinion Polls (by Noel Brinkerhoff and Steve Straehley, AllGov)