This data biography includes information about who created this data, and how, where, when, and why it was collected. We (the Assessment, Policy Development, and Evaluation Unit at Public Health – Seattle & King County) created it to help you understand where the data comes from and its strengths and limitations. If you have any further questions, please don’t hesitate to reach out to us at data.request@kingcounty.gov!

Who collects the data? 

The Behavioral Risk Factor Surveillance System (BRFSS) is created in a partnership between the national Centers for Disease Control and Prevention (CDC) and the Washington State Department of Health. The CDC coordinates the survey, but it is conducted separately by each state. The Washington State Department of Health contracts with ICF International, who administers the survey to participants in Washington.  

Who owns the data? 

The data is owned by the Washington State Department of Health, who shares it with Public Health – Seattle & King County.  

How is the data collected?  

Most BRFSS data are collected through telephone interviews. Households are randomly selected from lists of potential phone numbers in an area, including landline and cell phone numbers. Calls are made seven days a week during both the daytime and the evening. Once a household is contacted, one adult is randomly selected to be interviewed. The average phone interview lasts about 25 minutes. Some respondents may also be contacted and invited to complete an online or paper version of the survey. Participation in the survey is voluntary, and data is collected anonymously.   

Who is included and excluded from the data?  

BRFSS collects data from adults ages 18 and older, so data about children and youth is provided by adults in their households. BRFSS is conducted in English and Spanish, so adults who are not comfortable being interviewed in one of those languages are excluded. BRFSS also collects data from people living in private residences (which includes college dormitories and RVs), so people living in group facilities such as group homes or nursing homes and incarcerated people are excluded.  

The fact that some potential participants may not be willing to answer a call from a phone number they don’t recognize, to spend time on the phone being interviewed, or to share information about themselves and their health behaviors (even anonymously) with a government representative may also create response bias.  

Where is the data collected? 

BRFSS data is collected independently by all fifty states and some other jurisdictions. The data we share, unless otherwise noted, are responses from King County residents.

Why is the data collected? 

BRFSS was designed to measure changes in health-related risk behaviors, chronic health conditions, and use of preventive services (like cancer screenings). It is an important source of health-related data and is the only survey of its kind that collects information on certain health factors like tobacco use and insurance coverage.  

How often is this data collected? 

BRFSS data are gathered on an ongoing basis, with updates to the survey questions happening every year. Over 1,000 people are interviewed each month in Washington. However, not every question or topic is included every year.  

What else is important to know about this data?  

To ensure that the data we share better represent King County residents, we use weighting when analyzing these data. Weighting is a statistical process used to adjust any demographic (e.g. race/ethnicity, age, or gender) imbalances between survey respondents and the broader population that they represent (for example, adults in King County). This way, results will be generalizable to all King County adults, not just those who participate in BRFSS. This is a common approach used by nearly all large-scale population-based surveys. You can learn more about weighting here.  

The Centers for Disease Control and Prevention and the Washington State Department of Health are evaluating new approaches to BRFSS data collection, such as increasing the use of online surveys, that may change data collection methods in the near future.  

Where can I learn more about this data?  

You can view data for King County from BRFSS at https://kingcounty.gov/depts/health/data/community-health-indicators/behavioral-risk-factor-surveillance-system.aspx.  

You can find more information about BRFSS or request data files from the Washington State Department of Health and the Centers for Disease Control and Prevention.  

About data privacy and security 

The Assessment, Policy Development, and Evaluation Unit takes data security and the privacy of all individuals represented in our data very seriously. Data are stored in a secure environment.  For data sets that are not publicly available, only authorized staff are able to access them. Each data set has privacy guidelines to prevent sharing any information that may be identifiable – for example, not sharing (sometimes called suppressing) numbers when they are very small.