Muslim American Survey, 2011

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In 2007, the Pew Research Center conducted the first-ever nationwide survey of Muslim Americans. As the 10th anniversary of 9/11 approached, it seemed an appropriate time to survey Muslim Americans again and take stock of any important changes in the attitudes, opinions and experiences of this growing segment of U.S. society. The 2011 survey repeats many key questions from the 2007 poll. It also closely follows the methodology of the previous survey, including the use of random-digit-dialing to screen a large number of households (more than 41,000) to obtain a representative national sample of Muslims. As in 2007, interviews were conducted not only in English but also in Arabic, Urdu and Farsi, helping to ensure coverage of parts of the heavily immigrant Muslim American population that could be missed by an English-only survey.

The Pew Research Center study was able to complete interviews with 1,033 Muslim American adults 18 years old and older from a probability sample consisting of three sampling frames. Interviews were conducted by telephone between April 14 and July 22, 2001 by the research firm Abt SRBI.

Data File
Cases: 1,033
Variables: 214
Weight Variable: WEIGHT
Data Collection
Date Collected: April 14 - July 22, 2011
Original Survey (Instrument)
Muslim American Survey 2011
Funded By
The Pew Charitable Trusts
Collection Procedures
Interviews were conducted by telephone between April 14 and July 22, 2011 by the research firm of Abt SRBI. Interviews were conducted in English, Arabic, Farsi and Urdu. A total of 925 interviews were conducted in English, 73 in Arabic, 19 in Farsi and 16 in Urdu.
Sampling Procedures
"In random digit dial (RDD) surveys of the English-speaking U.S. population, roughly one-half of one percent of respondents typically identify as Muslim in response to a question about religious tradition or affiliation (or about 5 out of every 1,000 respondents). This extremely low incidence means that building a probability sample of Muslim Americans is difficult and costly. The demographic diversity of the population - especially with respect to race and national origins - adds to the challenge. Moreover, analysis of the 2007 survey and other previous research indicates that the Muslim population is not concentrated in a few enclaves but is highly dispersed throughout the U.S. and since 2007 the proportion of people who can be reached only by cell phone has grown.

"The sample design attempted to address the low incidence and dispersion of the Muslim American population, as well as cell phone coverage, by employing three sampling sources: an RDD landline sample, an RDD cell phone sample and a sample of previously identified Muslim households.

"1. Landline RDD: The landline RDD frame was divided into five strata, four of which were based on the estimated density of the Muslim population in each county of the United States as determined through an analysis of Pew Research's database of more than 260,000 survey respondents and U.S. Census Bureau data on ethnicity and language. To increase efficiency of the calling, the lowest density stratum - estimated to be home to approximately 8%-19% of U.S. Muslims - was excluded. A disproportionate sampling strategy was employed to maximize the effective sample size from the other three geographic strata; a total of 131 interviews were completed in the three strata included. The fifth stratum was a commercial list of 608,397 households believed to include Muslims, based on an analysis of first and last names common among Muslims. This stratus yielded completed interviews with 501 respondents.

"2. Cellular RDD: The cellular RDD frame was divided into the same four geographic strata as the landline RDD frame based on the estimated density of the Muslim population. As with the landline frame, the lowest density stratum was excluded in order to increase data collection efficiency. All Muslim adults reached in the cell sample were interviewed, regardless of whether or not they also had a landline. The fact that people with both types of phones had a higher chance of selection was adjusted for in the weighting as discussed below. The incidence rate of Muslim Americans was roughly three times higher in the cell frame than the landline frame (excluding the list stratus). A total of 227 interviews were completed in the cell RDD frame.

"3. Recontact sample: In addition, a sample of previously identified Muslim households was drawn from Pew Research Center's interview database and other RDD surveys conducted in recent years. This sample contained both landline and cell phone numbers. Recontacting these respondents from prior surveys yielded 174 completed interviews for this study.

"The strength of this research design was that it yielded a probability sample. That is, each adult in the U.S. had a known probability of being included in the study. The fact that some persons had a greater chance of being included than others (e.g., because they live in places where there are more Muslims) is taken into account in the statistical adjustment described below.

"RDD Geographic Strata
Pew Research Center surveys conducted in English (and some with a Spanish option) typically encounter about five Muslim respondents per 1,000 interviews, an unweighted incidence rate of 0.5%. The rate is also very similar to that encountered by other national surveys (for instance, see Tom Smith's "The Muslim Population of the United States: The Methodology of Estimates" in Public Opinion Quarterly, Fall 2002). This low incidence means that the costs of building an RDD sample of Muslim Americans by screening a general public sample are prohibitive. Accordingly, it was necessary to develop alternative approaches that would allow for estimation of the probabilities of selection but increase the yield from screening.

"An analysis of the geographic distribution of the Muslim population was undertaken, using several difference sources of data. A key resource was the Pew Research Center database of more than 260,000 telephone interviews conducted between 2007 and 2011; it was used to estimate the density of Muslims in each U.S. county. Another resource was data from the American Community Survey (ACS), which is the U.S. Census Bureau's replacement for the decennial census long form. The Census Bureau does not collect information about religion, but the ACS does include measures of ancestry, nationality for immigrants, and languages spoken. These measures were used to analyze the geographic distribution of adults who are from (or whose ancestors are from) countries with significant or majority Muslim populations, or who speak languages commonly spoken by Muslims. This yielded additional county-level estimates of the density of Muslims.

"These measures were highly correlated and were used to sort counties into four different groups based on the estimated incidence of Muslims in each county. We refer to these mutually exclusive groups as the geographic strata. The lowest density stratum accounts for 8% of all Muslim interviews conducted by the Pew Research Center over the past five years; the second lowest accounts for 30% of Muslim interviews; the medium density stratum accounts for 38%; and the highest density stratum accounts for 24%. Drawing on the analysis of previous Pew Research Surveys, ACS data, and the results of a piolt test, an optimal sampling allocation plan was developed for the RDD geographic strata. In total, 41,599 screening interviews in the RDD geographic strata were completed: 21% in the high density stratum, 52% in the medium density stratum and 27% in the low density stratum.

"The lowest density stratum, which included 8% of all U.S. Muslims in Pew Research surveys (and up to 19% as based on estimates derived from ACS data), also includes 45% of the total U.S. population. As a practical matter, the analysis of the Pew Research database indicated that 15,000 screening interviews would have to be conducted in this stratum to yield an estimated 10 Muslim respondents. In order to put the study's resources to the most efficient use, this stratus was excluded from the geographic strata of the RDD sample design, although persons living in these counties were still covered by the list stratum and recontact frame (a total of 113 interviews were completed in the lowest density areas from the list statum and recontact frame).

"List Stratum
Within the landline RDD frame of U.S. telephone numbers, a targeted, commercial list was used to identify 608,397 numbers that had a relatively high probability of belonging to a household with a Muslim adult. This list was defined as its own stratum within the landline RDD frame. This list was constructed from a commercial database of households where someone in the household has a name commonly found among Muslims. The list prepared by Experian, a commercial credit and market research firm that collects and summarizes data from approximately 113,000,000 U.S. households. The analysis of names was conducted by Ethnic Technologies, LLC, a firm specializing in multicultural marketing lists, ethnic identification software, and ethnic data appending services. According to Experian, the analysis uses computer rules for first names, surnames, and surname prefixes and suffixes, and geographic criteria in a specific order to identify an individual's ethnicity, religion and language preference.

In 2011, Abt SRBi purchased Experian's database of more than 608,000 households thought to include Muslims. This list consists of contact information, including telephone numbers. A test of the list, combined with the results of the screening interviews conducted in the course of the main survey, found that the Experian list was a highly efficient source for contacting Muslims; roughly three-in-10 households screened from the Experian list included an adult Muslim. The list does not, however, by itself constitute a representative sample of American Muslims. Muslims on the Experian list are somewhat better educated, more likely to be homeowners, more likely to be foreign born and of South Asian descent and much less likely to be African American or to have converted to Islam compared with Muslim Americans as a whole.

"By combining the Experian list with the RDD frame, however, the list can be used as one component of a probability sample. All telephone numbers drawn for the geographic strata of the landline RDD frame were compared to the entire Experian list of numbers. Any numbers that appeared in both the landline RDD geographic sample and the Experian list were removed from the former, and were available to be sampled only as part of the list stratum. This method makes it possible to determine the probability that any given Muslim has of being sampled, regardless of whether he or she is included in the Experian list. It also permits estimation of the proportion of all Muslims in the U.S. who are covered by the Experian list, which in turn makes it possible, in the final analysis, to give cases from the Experian sample an appropriate weight. More details on the statistical produces used to incorporate the list into the overall sample are provided below.

"Recontact Frame
In addition to contacting and interviewing a fresh sample of Muslim Americans, the phone numbers of all Muslim households from previous Pew Research surveys conducted between 2007 and 2011 were called. Adults in these households were screened and interviewed in the same manner used for the RDD samples. No attempt was made to reinterview the same respondent from earlier surveys. Pew Research's survey partners, Abt SRBI and Princeton Survey Research Associates International (PSRAI), also provided lists of Muslims interviewed in the course of other national surveys conducted in recent years. In total, the recontact frame consisted of phone numbers for 756 Muslims (552 landline numbers and 204 cell phone numbers) interviewed in recent national surveys. From this frame, 262 households were successfully screened, resulting in 174 completed interviews with Muslims.

"The greatest strengths of the recontact frame are that it consists entirely of respondents originally interviewed in the course of nationally representative surveys based on probability samples and that it includes respondents who live in the geographic stratum that was excluded from the landline and cell RDD samples. However, there are also certain potential biases of the recontact frame. Perhaps most obviously, all of the households previously interviewed in the recontact frame were interviewed in English, or for a small number in Spanish. Another potential source of bias relates to the length of time between when respondents were first interviewed and the current field period; respondents still residing in the same household in 2011 as in an earlier year may represent a more established, less mobile population compared with those from households that could not be recontacted.

"Analysis of the survey results suggests that there are some differences between Muslims in the recontact frame and those in the landline and cell RDD frames. For example, Muslims from the recontact frame are more likely to be a homeowner, less satisfied with national conditions, and less likely to have worked with others in their community to solve a problem compared with Muslims as a whole. These differences, however, are not sufficiently large so as to be able to substantially affect the overall survey's estimates." (Muslim American Survey 2011 Topline)
Principal Investigators
The Pew Research Center for the People & the Press and the Pew Forum on Religion & Public Life, with advice and assistance from additional Pew Research staff.
Related Publications
Muslim Americans: Middle Class and Mostly Mainstream http://www.pewforum.org/2007/05/22/muslim-americans-middle-class-and-mostly-mainstream2/
Notes on Weighting
"Several states of statistical adjustment (weighting) were needed to account for the use of multiple sampling frames and higher sampling rates in certain geographic areas. The first stage involved identifying all of the adults (Muslims and non-Muslims) who completed the screener in the landline (geographic + list strata) and cell RDD samples. These cases were adjusted, based on their probability of being samples for the survey. This adjustment accounted for four factors: (1) the percent of telephone numbers that were sampled in the stratum; (2) the percent of telephone numbers sampled in the stratum for which eligibility as a working and residential number was not determined; (3) the percent of residential numbers that were completed screeners in the stratum; and (4) the number of eligible adults in the household." (Muslim American Survey 2011 Topline)

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