“Historically, phone-based surveys dominated as the method of choice among those looking for a representative sample of U.S. residents. However, the prevalence of cell-only households has changed that approach dramatically. In 2013, the CDC estimated that 39.4% of American households were cell only, a lifestyle particularly prevalent among the young and those in lower socioeconomic status groups.
Given the prevalence of cell-only homes, online panels specifically built to represent the U.S. population are now the standard approach. The Pew Research Center estimated that 86% of adults used in the Internet in 2013. Online panels do have biases, but these can be mitigated with an appropriate sampling and weighting strategy.” FAQ People for bikes survey
“Because of these limitations [bias, lack of access and no standard list], researchers use two main strategies for surveying the general population using the internet. One strategy is to randomly sample and contact people using another mode (mail, telephone or face-to-face) and ask them to complete a survey on the web. Some of the surveys may allow respondents to complete the survey by a variety of modes and therefore potentially avoid the undercoverage problem created by the fact that not everyone has access to the web. This method is used for one-time surveys and for creating survey panels where all or a portion of the panelists take surveys via the web (such as the GfK KnowledgePanel and more recently the Pew Research Center’s American Trends Panel). Contacting respondents using probability-based sampling via another mode allows surveyors to estimate a margin of error for the survey (see Why probability sampling for more information).” Internet surveys, Pew Research