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2014 Methodology Download PDF

The American Values Atlas (AVA) is a project of Public Religion Research Institute (PRRI). Results for all demographic, religious affiliation, and political affiliation questions were based on 52,741 bilingual telephone interviews (including 26,424 cell phone interviews) conducted between January 2, 2014 and January 4, 2015 by professional interviewers under the direction of SSRS. Results for all opinion questions on specific issues (e.g. abortion, immigration, and same-sex marriage) are based on a subset of 40,571 telephone interviews conducted between April 2, 2014 and January 4, 2015. The AVA was made possible by generous grants from The Ford Foundation and The Carnegie Corporation of New York.

Throughout 2014, roughly 1,000 interviews were completed each week, with about 500 interviews conducted among respondents on their cell phones. Each week, interviewing occurred over a five-day period, from Wednesday through Sunday. The selection of respondents within households was accomplished by randomly requesting to speak with the youngest adult male or female currently living in the household.

Data collection was based on stratified, single-stage, random-digit-dialing (RDD) of landline telephone households and randomly generated cell phone numbers. The sample was designed to represent the total U.S. adult population from all 50 states, including Hawaii and Alaska. The landline and cell phone samples were provided by Marketing Systems Group.

The weighting was accomplished in two separate stages. The first stage of weighting corrects for different probabilities of selection associated with the number of adults in each household and each respondent’s telephone usage patterns—telephone usage refers to whether respondents have only a landline telephone, only a cell phone or both types. In the second stage, sample demographics were balanced to match target population parameters for gender, age, education, race and Hispanic ethnicity, region (U.S. Census definitions), population density, and telephone usage. The population density parameter was derived from 2010 Census data. The telephone usage parameter came from an analysis of the July-December 2013 National Health Interview Survey. All other weighting parameters were derived from an analysis of the U.S. Census Bureau’s March 2014 Current Population Survey.

The sample weighting was accomplished using iterative proportional fitting (IFP), a process that simultaneously balances the distributions of all variables. Weights are trimmed so that they do not exceed 4.0 or fall below 0.25 to prevent individual interviews from having too much influence on the final results. The use of these weights in statistical analysis ensures that the demographic characteristics of the sample closely approximate the demographic characteristics of the target populations.

The margin of error for total sample is +/- 0.5 percentage points at the 95% level of confidence. The design effect for total sample is 1.3. In addition to sampling error, surveys may also be subject to error or bias due to question wording, context, and order effects.

Sample Sizes for States and Metro Areas

State Total Sample Issue Subsample
United States 52,741 40,571
Alabama 820 633
Alaska 338 290
Arizona 952 734
Arkansas 549 432
California 4,506 3,441
Colorado 927 731
Connecticut 565 442
Delaware 157 124
Florida 3,265 2,499
Georgia 1,657 1,292
Hawaii 195 163
Idaho 309 243
Illinois 1,822 1,414
Indiana 1,294 951
Iowa 681 523
Kansas 568 447
Kentucky 814 620
Louisiana 825 616
Maine 300 236
Maryland 975 724
Massachusetts 984 737
Michigan 1,670 1,248
Minnesota 1,035 796
Mississippi 536 418
Missouri 1,102 866
State Total Sample Issue Subsample
Montana 256 194
Nebraska 360 284
Nevada 434 321
New Hampshire 267 219
New Jersey 1,448 1,104
New Mexico 371 292
New York 3,502 2,745
North Carolina 1,864 1,416
North Dakota 180 143
Ohio 2,041 1,508
Oklahoma 737 578
Oregon 742 588
Pennsylvania 2,515 1,883
Rhode Island 191 144
South Carolina 837 649
South Dakota 164 125
Tennessee 1,200 920
Texas 3,575 2,807
Utah 516 400
Vermont 156 120
Virginia 1,517 1,175
Washington 1,133 871
West Virginia 452 333
Wisconsin 1,201 954
Wyoming 123 95
Metro Area Total Sample Issue Subsample
Atlanta 858 678
Boston 689 513
Charlotte 382 300
Chicago 1,243 954
Cincinnati 388 276
Cleveland 326 243
Columbus 326 239
Dallas 925 736
Denver 440 348
Detroit 644 498
Houston 802 636
Indianapolis 332 234
Kansas City 366 292
Las Vegas 309 229
Los Angeles 1,407 1,074
Miami 801 620
Milwaukee 325 267
Minneapolis-St. Paul 603 470
Nashville 279 229
New York 3,383 2,647
Orlando 348 253
Philadelphia 1,045 804
Phoenix 568 428
Pittsburgh 482 357
Portland 355 272
San Francisco 498 394
Seattle 470 354
St. Louis 491 389
Tampa-St. Petersburg 532 411
Washington, DC 937 700