The majority of analysis in this report is based on a Pew Research Center survey conducted between Jan. 27 and Feb. 16, 2015, among a sample of 461 U.S. adults ages 18 or older. The survey was conducted by the GfK Group using KnowledgePanel, its nationally representative online research panel. GfK selected a representative sample of 1,537 English-speaking panelists to invite to join the subpanel and take the first survey in January 2014. Of the 935 panelists who responded to the invitation (60.8%), 607 agreed to join the subpanel and subsequently completed the first survey (64.9%) whose results were reported in November 2014. This group has agreed to take four online surveys about “current issues, some of which relate to technology” over the course of a year and possibly participate in one or more 45- to 60-minute online focus group chat sessions. For the second survey whose results are reported here, 461 of the original 607 panelists participated. A random subset of the subpanel receive occasional invitations to participate in online focus groups. For this report, a total of 80 panelists participated in one of nine online focus groups conducted during January 2015. Sampling error for the total sample of 461 respondents is plus or minus 5.8 percentage points at the 95% level of confidence.
The detailed discussion that follows is for the primary survey of 461 adults:
KnowledgePanel members are recruited through probability sampling methods and include both those with internet access and those without. KnowledgePanel provides internet access for those who do not have it and, if needed, a device to access the internet when they join the panel. A combination of random digit dialing (RDD) and address-based sampling (ABS) methodologies have been used to recruit panel members (in 2009 KnowledgePanel switched its sampling methodology for recruiting panel members from RDD to ABS). The panel comprises households with landlines and cellular phones, including those only with cellphones and those without a phone. Both the RDD and ABS samples were provided by Marketing Systems Group (MSG).
KnowledgePanel continually recruits new panel members throughout the year to offset panel attrition as people leave the panel. Respondents were selected randomly from eligible adult household members of the panel. All sampled members received an initial email on Aug. 5, 2014, to notify them of the survey and included a link to the survey questionnaire. One standard follow-up reminder was sent three days later to those who had not yet responded.
The final sample for this survey was weighted using an iterative technique that matches gender, age, education, race, Hispanic origin, household income, metropolitan area, and region to parameters from the March 2013 Census Bureau’s Current Population Survey (CPS). In addition, the sample is weighted to match current patterns of internet access from the October 2012 CPS survey. This weight is multiplied by an initial base or sampling weight that corrects for differences in the probability of selection of various segments of the sample and by a panel weight that adjusts for any biases due to nonresponse and noncoverage at the panel recruitment stage (using all of the parameters mentioned above as well home ownership status).
Sampling errors and statistical tests of significance take into account the effect of weighting at each of these stages. Sampling error for the total sample of 461 respondents is plus or minus 5.8 percentage points at the 95% level of confidence. The following table shows the unweighted sample sizes and the error attributable to sampling that would be expected at the 95% level of confidence for different groups in the survey:
Sample sizes and sampling errors for other subgroups are available upon request. The margins of error reported and statistical tests of significance are adjusted to account for the survey’s design effect, a measure of how much efficiency is lost from the weighting procedures. In addition to sampling error, one should bear in mind that question wording and practical difficulties in conducting surveys can introduce error or bias into the findings of opinion polls.
Pew Research Center is a nonprofit, tax-exempt 501(c)3 organization and a subsidiary of The Pew Charitable Trusts, its primary funder.
