Sampling for Internet Surveys

Sampling for Internet-based surveys involves first identifying a population of Internet users who will volunteer (often they are provided incentives for completing surveys) and then taking a sample of this population. Organizations such as GfK (formerly Knowledge Networks) recruit Internet users as potential survey respondents. When a client approaches GfK with an Internet survey, GfK will then take a sample of their potential respondents and invite those people to participate in the survey.

Samples of potential respondents are taken in a variety of ways. For the 2012 ANES, GfK used two sampling techniques — random digit dialing (RDD) and address-based sampling (ABS). In the context of this survey, potential respondents were called via telephone and asked if they would like to participate in the Internet-based survey. Those who did not have a computer and Internet service were provided with a laptop and service for use in the survey (the laptop was returned to GfK at the end of the study). Because pure RDD sampling can miss some respondents through such things as do-not-call lists and caller ID devices, and also because ANES did not want to contact potential respondents via cell phones, ANES asked GfK to augment the RDD sample with an address-based sample (ABS). Using the US Postal Service's Delivery Sequence File, randomly selected addresses were invited to join GfK's Knowledge Panel. Again, respondents lacking a computer were provided with one. GfK began recruiting people through ABS for the 2012 ANES in April, 2009.