Internet Polls Are Still Unreliable: Study

Polls are a bedrock of how we understand Americans' political opinions. But the fast growth of Internet-based surveys has been haunted by a fundamental problem: There is simply no way to draw a statistically random sample through the Internet. And that's really the classical requirement for ensuring accurate results.

But a new study by the Pew Research Center suggests that the problem could be overcome - and it's a finding that could have big implications for the use of Internet-based polls going forward.

The report isn't quite good news for Internet polling; it found large average errors across 8 of the 9 web survey companies tested, in fact. Such samples are called "non-probability" samples since respondents are drawn through pools of volunteers who often receive rewards or other incentives for taking surveys. Because not every person in the population has a chance of being selected for the survey (volunteers self-select), they cannot be statistically projected to the population within a traditional margin of sampling error. Many news organizations, including The Post, avoid reporting on their results for this reason.

Most strikingly, Pew found its Internet-based American Trends Panel was not especially accurate on overall measures, despite the fact respondents were initially recruited through traditional "probability-based" telephone sampling. Equally surprising is that one of the volunteer web panels outperformed all others. By a lot.

The study also contained some sobering results for web surveys' ability to accurately represent African-American and Hispanic respondents. That finding is significant, since one of the biggest ambitions of web-sampled surveys is accurately representing a smaller demographic of the population, like a racial minority, that is prohibitively expensive to interview using traditional methods.

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