The analysis in this report is based on a Pew Research Center survey conducted in association with A+E Networks’ HISTORY. The survey was conducted June 16-July 4, 2016, among a sample of 2,025 adults, ages 18 and older. The survey was conducted by the GfK Group using KnowledgePanel, its nationally representative online research panel. KnowledgePanel members are recruited through probability sampling methods and include individuals both with and without internet access. 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. The panel includes 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. The survey was conducted in English and Spanish.

All active members of the GfK panel were eligible for inclusion in this study. In all, 3,333 panelists were invited to take part in the survey. All sampled members received an initial email to notify them of the survey and provide a link to the survey questionnaire. Additional follow-up reminders were sent to those who had not yet responded as needed.

The final sample of 2,025 adults was weighted using an iterative technique that matches gender and, within gender, age, race/ethnicity, education, region, household income, home ownership status and metropolitan area to parameters from the March 2015 Census Bureau’s Current Population Survey (CPS). In addition, the sample is weighted to match current patterns of internet access from the Current Population Survey. This weight is multiplied by an initial sampling or base weight that corrects for differences in the probability of selection of various segments of GfK’s 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 described above). Details about the GfK panel-level weights can be found in this document.

Sampling errors and statistical tests of significance take into account the effect of weighting at each of these stages. The margin of sampling error at the 95% confidence level is plus or minus 2.3 percentage points for results based on the full sample (n=2,025). Sample sizes and sampling errors for other subgroups are as follows:

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.