BRFSS Methodology

Questionnaire Development

The BRFSS questionnaire three sections:

1. Core Component: The fixed core contains standard questions that are asked by every state each year. There is also a rotating core, which consists of questions that are collected every other year by every state. In off years, the rotating core questions are offered as optional modules.
2. Optional Modules: Each year, the CDC offers a selection of standardized optional modules that states can elect to add to their questionnaire. Data processing for optional modules is completed by the CDC. The CDC requires that, if the modules are used, they must be used in their entirety without any modification. If optional modules are altered, they are considered state-added questions (see below).
3. State-Added Questions: These are questions of special interest to the state that are not offered as optional modules. The 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 health issues.

Sometimes, there is an emerging core. It is set up as one to five questions that are added to either the fixed or rotating cores. These are usually time-sensitive, topical questions. An example of an emerging core question would be one to collect information on a nationwide outbreak.

Each summer, the BRFSS Coordinator contacts Iowa Department of Public Health (IDPH) program managers to invite them to request questions that benefit program efforts to be included in the survey for the following year. Requested questions can include optional CDC modules or state-added questions which are developed by programs to address data needs that may not be addressed through CDC core questions or optional modules. The Iowa BRFSS program understands the importance of the inclusion of program-specific questions in the survey, however, available space to include state-added questions is limited.

Once requests for all state-added questions/modules for an upcoming survey year are collected, the IDPH BRFSS Advisory Group reviews the requests and selects questions determined by IDPH priorities. The committee considers factors such as how well the questions will work in a telephone survey, how recently the questions have been asked in past surveys, how the program plans to use the collected data, and how the questions align with the Department’s strategic plan and Iowa’s top health issues. The committee’s recommendations are ultimately approved by the IDPH Deputy Director.

Sampling

The BRFSS is a telephone-based survey. The BRFSS collects data from adults aged 18 years or older. Households are randomly selected from blocks of potential phone numbers in an area (including unlisted numbers). One adult in the household is randomly selected to be interviewed. Participants are chosen at random to ensure that the collected data is generalizable to the state as a whole.

Weighting

Once responses are compiled, the CDC analyzes the demographic characteristics of the sample and assigns weights to each of the responses to ensure estimates are reflective of the known population. This weighting allows us to generalize the results of the BRFSS survey to the population as a whole. Because some groups are harder to reach than others, the CDC also weights to compensate for non-selection or non-response bias. In other words, the CDC adjusts for over-representation or under-representation of certain groups in the sample.