Appendix 1: Survey Methodology
report includes survey data from several sources, including newly released
results from a survey conducted June 28-July 9, 2012, by the Pew Research
Center for the People & the Press and the Pew Research Center’s Forum on
Religion & Public Life, among a national sample of 2,973 adults. The new
survey is based on telephone interviews among adults 18 years of age or older living in all 50 U.S. states
and the District of Columbia (1,771
respondents were interviewed on a landline telephone, and 1,202 were
interviewed on a cell phone, including 596 who had no landline telephone). The
survey was conducted by interviewers at Princeton Data Source and Universal
Survey Center under the direction of Princeton Survey Research Associates
International. A combination of landline and cell phone random digit dial
samples were used; both samples were provided by Survey Sampling International.
Interviews were conducted in English and Spanish. Respondents in the landline
sample were selected by randomly asking for the youngest adult male or female
who is now at home. Interviews in the cell sample were conducted with the
person who answered the phone, if that person was an adult 18 years of age or
older. For detailed information about our survey methodology, see http://people-press.org/methodology/.
combined landline and cell phone sample are weighted using an iterative
technique that matches gender, age, education, race, Hispanic origin and
nativity and region to parameters from the March 2011 Census Bureau's Current
Population Survey and population density to parameters from the Decennial
Census. The sample also is weighted to match current patterns of telephone
status and relative usage of landline and cell phones (for those with both),
based on extrapolations from the 2011 National Health Interview Survey. The
weighting procedure also accounts for the fact that respondents with both
landline and cell phones have a greater probability of being included in the
combined sample and adjusts for household size among respondents with a
partnership with Religion & Ethics NewsWeekly, the Pew Forum conducted an
additional 511 interviews with religiously unaffiliated adults to produce a
total sample of 958 unaffiliated respondents. These 511 additional interviews were
conducted June 28-July 10, 2012, with religiously unaffiliated adults recruited
by screening respondents from a fresh sample of landline and cell phone RDD phone
numbers (261 interviews) and by recontacting respondents from recent surveys
who had identified themselves as religiously unaffiliated (250 interviews).
These additional interviews are used only when reporting on the religiously
unaffiliated (including the unaffiliated subgroups – atheist, agnostic and
those who describe their religion as “nothing in particular”); these interviews
are not used when reporting results for the general public. For the RDD and
cell phone recontact samples, respondents were initially selected in the same
way as described above. For the landline recontact sample, interviewers asked
to speak with the person who, based on gender and age, participated in the
earlier survey. Once the selected respondents were on the phone, interviewers
asked them a few questions and then asked their religious affiliation; those
who are religiously unaffiliated continued with the remainder of the interview.
weighting procedure for the additional interviews with religiously unaffiliated
respondents used an iterative technique that included all of the parameters
described above. In addition, the weighting accounted for the oversampling of
unaffiliated respondents in the screened and callback samples, the type of
unaffiliated respondent (atheist, agnostic or “nothing in particular”), as well
as gender, age, region and the 2012 presidential vote preference among the
unaffiliated. The parameters for the type of unaffiliated respondent and for
gender, age and region among the unaffiliated are based on combined data from
Pew Research Center surveys conducted from July 2011-June 2012. The parameter
for the 2012 vote preference is based on the vote preferences of unaffiliated
respondents in the main June 28-July 9 sample.
total, the new survey includes 958 religiously unaffiliated respondents (447
from the main sample plus the 511 additional interviews). The following table
shows the sample sizes and the error attributable to sampling that would be
expected at the 95% level of confidence for key groups in this survey. Sampling
errors and statistical tests of significance take into account the effect of
sizes and sampling errors for other subgroups are available upon request.
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.
following questions on the survey were developed in consultation with Religion
& Ethics NewsWeekly: Q21a-b, Q22, Q51-54 Q70, Q72, Q73a-g and Q97a-b.
report also includes analysis of past survey data, including aggregated data
from Pew Research Center surveys conducted over months or years, data from
individual past Pew Research Center surveys and data from surveys conducted by
other organizations. Full details on previous Pew Research Center surveys are
available at www.pewresearch.org.