November 12, 2014

Public Perceptions of Privacy and Security in the Post-Snowden Era

Methods

About this survey

The analysis in this report is based on a survey conducted January 10-27, 2014 among a sample of 607 adults, 18 years of age 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. 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%). 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 45-60-minute online focus group chat sessions. A random subset of the subpanel receive occasional invitations to participate in these online focus groups. For this report, a total of 26 panelists participated in one of three online focus groups conducted during August 2013 and March 2014.

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 cell phones, 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.19 All sampled members received an initial email on January 10, 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 or not, 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 607 respondents is plus or minus 4.6 percentage points at the 95% level of confidence.20 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.

  1. When a household is selected to be invited to KnowledgePanel, GfK attempts to enroll the entire household (age 14+). Subsequent samples from the full KnowledgePanel are then selected using a “one member per household” criterion to avoid clustering affects.
  2. The original margin of error provided by the vendor and published here (3.98) used a less conservative design effect. However, the analysis in the report was based on the more conservative design effect and the significance of the findings is not affected by this change.