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.
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.
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.
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.
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.
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.
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
8. What are the components of the BRFSS questionnaire?
The BRFSS questionnaire has three parts: (1) the core, (2) optional modules, and (3) state-added questions. All states must ask the core questions without modifying wording or question order. Core sections are supported financially by the Centers for Disease Control and Prevention (CDC). Optional modules or state-added questions are included on the questionnaire at a cost determined by the BRFSS Coordinator and paid for by the requestor.
Core
Fixed Core: The fixed core is a standard set of questions asked every year. It includes questions about health status, behaviors that affect health (e.g., tobacco and alcohol use), and questions on demographic characteristics. Rotating Core: The rotating core is made up of two distinct sets of questions, each asked in alternating years by all states, addressing different topics. In the years that rotating topics are not used in the core, they are supported as optional modules.Emerging Core: The emerging core is a set of up to five questions that are added to the fixed and rotating cores. Emerging core questions typically focus on issues of a "late breaking" nature and do not necessarily receive the same scrutiny that other questions receive before being added to the instrument. These questions are part of the core for two years. See CDC questionnaire archive to search all questions that have been included in the core or optional modules since 1984.
Optional Modules
Optional modules are standardized sets of questions on specific topics that states elect to use on their questionnaires. Modules include a wide variety of topics such as, oral health, violence, cardiovascular disease, and environmental toxins. CDC standards require that, if the modules are used, they must be used without modification. If optional modules are altered, they are considered state-added questions. See Optional Modules by State or Category to see which optional modules were included in each state's questionnaire for each year.
State Added Questions
State-added questions are any data item that is not part of the core or an unaltered optional module. CDC does not complete any of the data processing necessary for analysis of state added questions. Additionally, state added questions are not necessarily comparable to other states. However, state-added questions allow states the flexibility to address their unique issues.
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.
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.
11. If a local organization or agency wants to include questions on the BRFSS, how is this done?
The BRFSS questionnaire goes through rigorous testing before its use. Federal agencies submit proposals to the Division of Behavioral Surveillance (DBS) of CDC with a clear rationale for including questions in the core or optional modules.
A national questionnaire review committee, composed of a subgroup of state BRFSS coordinators, reviews the proposals and makes recommendations to the submitting agencies for changes prior to two rounds of cognitive testing of the new questions and field testing of the questionnaire. All BRFSS coordinators and DBS staff review the final versions of proposed questions at the annual BRFSS conference.
Similarly, requests for inclusion of additional data items on Montana's questionnaire are reviewed by the state BRFSS Coordinator in consultation with the Montana BRFSS Working Group.
Several criteria must be met in order to have questions added to the Montana BRFSS questionnaire. A written proposal must be submitted to the state BRFSS Coordinator (typically by mid-September) of the year preceding the survey. Members of the state BRFSS Working Group make recommendations regarding which questions or modules will be included in the survey. CDC approval is required to place any optional module or state-added question into the core section of the questionnaire; we will not add questions that may adversely affect the response rates of the survey.
Final decisions are at the BRFSS Coordinator's discretion based upon survey integrity.
If your agency or organization is interested in adding a question (or questions) to the BRFSS survey, please contact the BRFSS Coordinator at MTBRFSS@mt.gov for additional details.
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.
13. If I have questions about BRFSS, is there someone I may contact?
Yes! Contact Montana’s BRFSS Coordinator at MTBRFSS@mt.gov.