Results for the main Political Typology Survey are based on telephone interviews conducted under the direction of Princeton Survey Research Associates International among a nationwide sample of 2,000 adults, 18 years of age or older, during the period Dec. 1-16, 2004. For results based on the total sample, one can say with 95% confidence that the error attributable to sampling is plus or minus 2.5 percentage points. For results based on Form 1 (N=993) or Form 2 (N=1007) only, the error attributable to sampling is plus or minus 3.5 percentage points. For results based on abbreviated field periods, with sample sizes ranging from 419 to 523, the margin of error is plus or minus 5.5 percentage points.
The Typology Callback Survey obtained callback telephone interviews with 1,090 respondents from the December 2004 Typology survey from March 17 to March 27, 2005. Statistical results are weighted to correct known demographic discrepancies. The margin of sampling error for the recontacted respondents is plus or minus 3.5% percentage points.
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.
Survey Methodology In Detail
The sample for this survey is a random digit sample of telephone numbers selected from telephone exchanges in the continental United States. The random digit aspect of the sample is used to avoid “listing” bias and provides representation of both listed and unlisted numbers (including not-yet-listed). The design of the sample ensures this representation by random generation of the last two digits of telephone numbers selected on the basis of their area code, telephone exchange, and bank number.
The telephone exchanges were selected with probabilities proportional to their size. The first eight digits of the sampled telephone numbers (area code, telephone exchange, bank number) were selected to be proportionally stratified by county and by telephone exchange within county. That is, the number of telephone numbers randomly sampled from within a given county is proportional to that county’s share of telephone numbers in the U.S. Only working banks of telephone numbers are selected. A working bank is defined as 100 contiguous telephone numbers containing three or more residential listings.
The sample was released for interviewing in replicates. Using replicates to control the release of sample to the field ensures that the complete call procedures are followed for the entire sample.
At least 10 attempts were made to complete an interview at every sampled telephone number. The calls were staggered over times of day and days of the week to maximize the chances of making a contact with a potential respondent. All interview breakoffs and refusals were re-contacted at least once in order to attempt to convert them to completed interviews. In each contacted household, interviewers asked to speak with the “youngest male 18 or older who is at home.” If there is no eligible man at home, interviewers asked to speak with “the oldest woman 18 or older who is at home.” This systematic respondent selection technique has been shown empirically to produce samples that closely mirror the population in terms of age and gender.
Non-response in telephone interview surveys produces some known biases in survey-derived estimates because participation tends to vary for different subgroups of the population, and these subgroups are likely to vary also on questions of substantive interest. In order to compensate for these known biases, the sample data are weighted in analysis.
The demographic weighting parameters are derived from a special analysis of the most recently available Annual Social & Economic Supplement data from the Census Bureau (March 2003). This analysis produced population parameters for the demographic characteristics of households with adults 18 or older, which are then compared with the sample characteristics to construct sample weights. The analysis only included households in the continental United States that contain a telephone. The weights are derived using an iterative technique that simultaneously balances the distributions of all weighting parameters.
For the typology callback survey, as many as 10 attempts were made to contact each original survey respondent. Calls were staggered over times of day and days of the week to maximize the chance of making contact with potential respondents. Each household received at least one daytime call in an attempt to complete and interview. The 1,090 interviews represent a recontact rate of 55%.
Methodolgy for Creating the Typology
The value dimensions used to create the typology are each based on the combined responses to two or more survey questions. The questions used to create each scale were those shown statistically to be most strongly related to the underlying dimension. Each of the individual survey questions use a “balanced alternative” format that presents respondents with two statements and asks them to choose the one that most closely reflects their own views. To measure intensity, each question is followed by a probe to determine whether or not respondents feel strongly about the choice they selected.
As in past typologies, a measure of political attentiveness and voting participation was used to extract the “Bystander” group, people who are largely unengaged and uninvolved in politics. A statistical cluster analysis was used to sort the remaining respondents into relatively homogeneous groups based on the nine value scales, party identification, and self reported ideology. Several different cluster solutions were evaluated for their effectiveness in producing cohesive groups that are distinct from one another, large enough in size to be analytically practical, and substantively meaningful. The final solution selected to produce the new political typology was judged to be strongest on a statistical basis and to be most persuasive from a substantive point of view.