About the Research
About the Research
Throughout this book we refer to primary research that is not footnoted. These statistics and data-based analyses are derived from a series of national public-opinion surveys conducted by Barna Group.
Dates
Collection method
Sample size
Sampling error*
2009–2015
Cities
&
States
telephone and online
30,535
±0.5
November 2012
US adults
telephone
1,008
±2.9
July 2014
Christian clergy
telephone and online
±2.4
July 2014
Clergy from other faith traditions
telephone and online
159
±7.7
January 8–February 11, 2015
US adults
telephone and online
2,010
±2.0
April 29–May 1, 2015
US adults
online
1,025
±2.9
June 27–28, 2015
US adults
telephone
1,012
±2.9
July 3–9, 2015
US adults
online
1,237
±2.6
August 17–21, 2015
US adults
online
1,000
±3.0
August 24–26, 2015
US adults
online
1,000
±3.0
*Percentage points; sampling error reflects a 95-percent confidence level.
All of the research studies identified above, with the exception of the faith-leader research, were independently funded by Barna Group. The clergy research was conducted on behalf of the Maclellan Foundation.
Once data was collected, minimal statistical weights were applied to several demographic variables to more closely correspond to known national averages. On questions for which tracking was available, findings from these recent studies were compared to Barna’s database of national studies from the past three decades. Data from the clergy study were minimally weighted on denomination and region to more closely reflect the demographic characteristics of churches in each media market.
When researchers describe the accuracy of survey results, they usually provide the estimated amount of “sampling error.” This refers to the degree of possible inaccuracy that could be attributed to interviewing a group of people that is not completely representative of the population from which they were drawn. For the general population surveys, see the table above for maximum sampling error.
There is a range of other errors that can influence survey results (e.g., biased question wording, question sequencing, inaccurate recording of responses, inaccurate data tabulation, etc.)—errors whose influence on the findings cannot be statistically estimated. Barna makes every effort to overcome these possible errors at every stage of research.