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FAQ - Data Users

Frequently Asked Questions for Data Users

Important Notification for Survey Years 2011 and Beyond

Starting in 2011 BRFSS estimates can no longer be directly compared to estimates from previous years, causing a break in the trend line. All years going forward from 2011 can be compared to one another. New methodological changes of adding cell phone sampling and using a larger number of socio-demographics to weight the data greatly improves the accuracy, coverage, validity, and representativeness of BRFSS data, however it prevents comparisons to data using the prior survey methodology. For more information on these changes, please visit the CDC website.

1. What is the Behavioral Risk Factor Surveillance System (BRFSS)?
2. How is the BRFSS conducted?
3. How are BRFSS data weighted? And what post-stratification variables are used when weighting BRFSS data?
4. Who is interviewed?
5. What type of information does the BRFSS collect?
6. Is the information collected from each individual made public?
7. How are BRFSS data collected?
8. What are the components of the BRFSS questionnaire?
9. What is done with the information collected?
10. How are new questions added to the BRFSS questionnaire?
11. If a local organization or agency wants to include questions on the BRFSS, how is this done?
12. Where can I find out more about BRFSS and the ways its data are used?
13. If I have questions about BRFSS, is there someone I may contact?


1. What is the Behavioral Risk Factor Surveillance System (BRFSS)?
The BRFSS is a state-based system of telephone surveys conducted in collaboration with the Centers for Disease Control and Prevention (CDC) that gathers information about health, health risk behaviors, preventive practices, and health care access from adults aged 18 and older.

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2. How is the BRFSS conducted?
The BRFSS is a cross-sectional, continually ongoing random digit dialed (RDD) telephone survey conducted by states, with technical and methodological assistance provided by the CDC. Every year, states conduct monthly telephone surveys using a questionnaire developed collaboratively by states and the CDC. Monthly data are aggregated for each state and sent to CDC for weighting. The datasets are returned to the states at the end of each year for further data analyses.

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3. How are BRFSS data weighted? And what post-stratification variables are used when weighting BRFSS data?
BRFSS data are first weighted for the probability of selection of a telephone number, the number of adults in a household, and the number of telephones in a household. Then post-stratification adjustments are made to account for non-response and non-coverage (households without telephones). For the 2010 dataset and prior surveys post-stratification was based on only age, sex, and region of residence. Beginning with the 2011 dataset, a raking (or iterative proportional fitting) procedure is used for post-stratification adjustment. The use of raking procedures allows post-stratification adjustment to be based on twelve demographic dimensions rather than only three. For a complete explanation of raking procedures see the Montana Fact[or]s report, "Changing BRFSS Protocols: Transition to Raking Weights and Incorporation of Cell Phone Sampling?.

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4. Who is interviewed?
Adults 18 years or older who live in a private residence or a college housing unit are asked to take part in the survey. Only one adult per household is randomly selected to be interviewed once the telephone number is verified as a private working phone number. Cell phone numbers are also sampled allowing adults who receive at least 90% of their calls on their cell phone to be included in the sample. Participants are not compensated.

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5. What type of information does the BRFSS collect?
BRFSS interviewers ask questions related to behaviors that are associated with preventable chronic diseases, injuries, infectious diseases, and other health-related topics. General demographic information such as age, race, income, education, disability status, and sex are also collected. See Questionnaires link for specific yearly survey questions.

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6. Is the information collected from each individual made public?
Absolutely not! There is no personally-identifiable information associated with the respondent's answers. A fundamental principle of BRFSS is protecting the confidentiality of the respondent's answers. Answers to BRFSS questions are aggregated which means that no one individual's data can be traced back to a particular person. Even the telephone number called is not included in the dataset so that answers cannot be connected to a specific person or telephone number.

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7. How are BRFSS data collected?
Information is collected through telephone interviews throughout the survey year. A set of randomly generated phone numbers are produced at least four times per year, and the phone numbers are first called to verify if they are residential or a business phone number. If residential, a randomly selected adult in the household is asked to participate. This can result in repeat phone calls to the household in order to get the appropriate (randomly selected) adult to participate. In addition, the 2011 survey and all subsequent years must have at least 20% of the total completed interviews consist of responses from cell phone users. Adults who receive at least 90% of their calls on their cell phone are eligible to be included in the cell phone sample

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8. What are the components of the BRFSS questionnaire?
The BRFSS questionnaire has three parts: (1) the Core section, (2) Optional modules, and (3) State-added questions. All states must ask the core questions without modification in wording. Core sections and possibly emerging issues are the only ones supported financially by the Centers for Disease Control and Prevention (CDC). States may use optional modules if they wish, with or without modification. CDC will produce state-to-state prevalence estimate comparisons of core and unmodified optional modules. Optional modules or state-added questions are included on the questionnaire at a cost determined by the BRFSS Director and paid for by the requestor.

Fixed core questions are asked every year. Rotating core questions are asked every other year. Emerging core questions typically focus on late-breaking health issues. These questions are evaluated at the end of a survey year to determine if they are valuable. If the CDC and the state BRFSS Coordinators decide to keep the questions, they are added to the fixed core, rotating core, or optional modules in subsequent years.

The optional modules are standardized questions that cover additional health topics or are more detailed questions on a health topic included in the core. Each year states must choose which optional modules they will use based on the data needs of their state.

Emerging Issues may also be included in the BRFSS survey on an as-needed basis. For example, BRFSS was able to mobilize in October 2004 and field 4 months of additional flu vaccination questions in order to assess the nationwide flu vaccine shortage that occurred in the 2004 - 2005 flu season.

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9. What is done with the information collected?
BRFSS information is used to:

  • identify emerging health problems
  • establish and track health objectives
  • develop, implement, and evaluate a broad array of disease prevention activities
  • support health-related policy decisions.

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10. How are new questions added to the BRFSS questionnaire?
The content of the BRFSS core questionnaire is determined by the state BRFSS Coordinators and the CDC. Each year, the state Coordinators may choose to add new questions based on proposals submitted before the annual BRFSS conference. Each proposal requires a rationale supporting the questions. If questions are approved by the state BRFSS coordinators, the questions then go through technical review, cognitive testing, and field testing before being placed on the questionnaire. In addition, each state has the opportunity to customize its questionnaire by adding questions that address its unique health issues. See the following question for further explanation.

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11. If a local organization or agency wants to include questions on the BRFSS, how is this done?
There is an established process for including additional data items to the Montana questionnaire. All requests for additional data items must be submitted electronically to the state BRFSS Coordinator in August (typically) of the year preceding the upcoming year's BRFSS survey. Visit the MT Working Group page for more detail and to download the Criteria and Procedures for Addition of Survey Questions brochure.

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12. Where can I find out more about BRFSS and the ways its data are used?
On this site, you will find a rich variety of reports, publications, maps, and even access BRFSS data itself in the Results section. The CDC BRFSS website provides detailed technical information, data quality reports, results from other state's BRFSS, and public use data sets which can be downloaded.

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13. If I have questions about BRFSS, is there someone I may contact?
Yes! Contact the state BRFSS coordinator. See the left panel of this page to find a variety of ways to get in touch.

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