Methodology › 2017 Methodology

2017 Methodology

The 2017 American Values Atlas (AVA) is a project of PRRI. Results for all demographic, religious affiliation, and political affiliation questions were based on 71,197 bilingual telephone interviews (including 42,548 cell phone interviews) conducted between January 4, 2017 and December 30, 2017 by professional interviewers under the direction of SSRS. Results for questions on specific issues (e.g. LGBT issues) are based on a subset of 40,017 telephone interviews (including 23,903 cell phone interviews) conducted between April 5, 2017 and December 23, 2017. The AVA was made possible by generous grants from The Carnegie Corporation of New York, The Evelyn and Walter Haas, Jr. Fund, The Gill Foundation, and The Nathan Cummings Foundation.

Throughout 2017, at least 1,000 interviews were completed each week, with about 600 interviews conducted among respondents on their cell phones. Each week, interviewing occurred over a five-day period, from Wednesday through Sunday or from Thursday through Monday. 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. 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 January-June 2017 National Health Interview Survey. All other weighting parameters were derived from an analysis of the U.S. Census Bureau's March 2017 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 table below shows the sample sizes for all 50 states and 30 metro areas for both sample and issue subsample. The margin of error for total sample is +/- 0.4 percentage points at the 95% level of confidence. The margin of error for issue subsample is +/- 0.6 percentage points at the 95% level of confidence. The design effect for both total sample and the issue subsample is 1.4. 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 71,197 40,017
Alabama 1,100 624
Alaska 287 156
Arizona 1,444 792
Arkansas 641 340
California 7,260 3,942
Colorado 1,210 631
Connecticut 659 385
Delaware 219 167
Florida 4,374 2,495
Georgia 2,171 1,186
Hawaii 298 163
Idaho 461 264
Illinois 2,452 1,387
Indiana 1,531 928
Iowa 895 500
Kansas 686 372
Kentucky 1,017 559
Louisiana 983 578
Maine 359 198
Maryland 1,220 700
Massachusetts 1,280 698
Michigan 2,348 1,354
Minnesota 1,412 787
Mississippi 586 303
Missouri 1,505 845
State Total Sample Issue Subsample
Montana 348 195
Nebraska 519 285
Nevada 832 491
New Hampshire 311 181
New Jersey 1,774 979
New Mexico 534 304
New York 4,548 2,548
North Carolina 2,499 1,385
North Dakota 247 157
Ohio 2,750 1,524
Oklahoma 794 434
Oregon 1,130 664
Pennsylvania 3,278 1,792
Rhode Island 222 164
South Carolina 1,116 608
South Dakota 259 165
Tennessee 1,480 808
Texas 4,944 2,813
Utah 732 370
Vermont 212 168
Virginia 1,955 1,120
Washington 1,762 1,036
West Virginia 503 282
Wisconsin 1,522 855
Wyoming 236 170
Metro Area Total Sample Issue Subsample
United States 71,197 40,017
Atlanta 1,159 631
Boston 841 445
Charlotte 538 290
Chicago 1,735 970
Cincinnati 523 306
Cleveland 466 268
Columbus 459 246
Dallas 1,247 710
Denver 584 297
Detroit 926 539
Houston 1,055 584
Indianapolis 491 285
Kansas City 514 279
Las Vegas 606 360
Los Angeles 2,247 1,176
Miami 1,062 618
Milwaukee 399 222
Minneapolis-St. Paul 878 474
Nashville 353 182
New York 4,183 2,314
Orlando 449 242
Philadelphia 1,428 805
Phoenix 907 501
Pittsburgh 660 372
Portland 583 347
San Francisco 833 472
Seattle 782 464
St. Louis 726 422
Tampa-St. Petersburg 666 402
Washington, DC 1,396 799