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  1. An Overview of the North Carolina Behavioral Risk Factor Surveillance System (BRFSS) Presentation to the State Health Director's Conference January 23, 2014 State Center for Health StatisticsDivision of Pubic HealthNC Dept. of Health & Human Services

  2. Presentation Outline • How the survey is done • Questionnaire development • Sampling • Data Collection • Weighting • Future developments • Demonstrate how to access results • Q&A State Center for Health StatisticsDivision of Pubic HealthNC Dept. of Health & Human Services

  3. Timeline for 2014 BRFSS 2012 External review of proposed new/revised questions 2013 State Coordinators vote on proposed questions CDC field tests questionnaire CDC Core & Optional Modules checked and finalized State-added questions reviewed and finalized CATI coding developed and checked Interviewers trained 2014 Conduct interviews January through December 2015 CDC sends final weighted data to NC SCHS reviews data and produce web tables

  4. BRFSS QuestioNnaire

  5. Questionnaire Organization • Each years survey is divided into three main parts CDCOptionalModules State-AddedQuestions CDCCoreQuestions Developed by eachstate’s coordinator Mandated by CDC;must ask all questions exactly as written States choose whichmodules they willadminister; must askall questions exactlyas written

  6. The Core • The CDC Division of Behavioral Surveillance (DBS) works with other CDC programs to develop questions for the core & optional modules • Proposed questions undergo two rounds of cognitive testing • State Coordinators have input via • Participation in State Working Group • Participation as external reviewer for proposed questions • Vote on proposed questions taken at Annual Conference • Questions rotate in & out of core on a fixed schedule • Just adopted a new 5-year plan for the core

  7. CDC Optional Modules • Process for developing optional modules is similar to the core • CDC programs pay DSB for space on the BRFSS • So the selection of optional modules available varies each year

  8. State-Added Questions • May include • Questions from other surveys, including questions on CDC Optional Modules • Questions written by state staff • Each state has a process for soliciting proposed questions

  9. Survey time is a very scarce resource • When telephone interviews run past 15 to 20 minutes, • Break-offs increase • Data quality suffers as people say whatever comes to mind so you’ll leave them alone! • Some cell phone respondents are more sensitive to length because they pay by the minute • Pew Research Center successfully does 20 minute cell phone interviews

  10. The 2013 NC BRFSS interview averaged 29 minutes • 17 minutes of that is take up by Core questions and an expanded Optional Module on Health Care Access • “Core creep” – expansion of the length of the core – is a major issue with state coordinators • We have been trying to cut down on state-added and CDC Optional Modules to shorten the interview


  12. Random Digit Dialing (RDD) Surveys • 4 digit numbers are generated at random within each combination of area code and phone exchange within a geographic area • Resulting numbers are screened to identify non-working numbers • Results in a random sample of telephone numbers for a given geographic region

  13. BRFSS uses a Dual-Frame RDD Sample • Landline Frame • Numbers generated within area code/exchange combinations for landline telephones • Telco companies share more information regarding these numbers • Most importantly where the phone is located

  14. Cell Phone Frame • Numbers generated within area code/phone exchange combinations for cell phones • Cell phone companies share little information about these numbers • Little information on where owner of phone lives until they are interviewed

  15. Increase in “Cell Phone Only” (Wireless) Households • Roughly 38% of adults as of the end of 2013. • These folks are: • Younger • More are minorities • Less affluent • Have some significantly different health conditions & behaviors • Must sample this population to avoid biased estimates

  16. Data collection

  17. “BRFSS is a process, not a project” • Survey runs throughout calendar year • Each month we receive separate landline and cell phone samples (~8,000 phone numbers total) • To complete each month’s “study” • Each landline number is called up to 15 times • Each cell phone number is called up to 8 times • We call seven days a week around 330 days every year

  18. More difficult to reach cell phone respondents • In the landline sample • Get one completed interview every 1.4 hours of interview time • Perform 38 dialings per completed interview • 4,600 sample records yield ~900 completed interviews • Cell • Get one completed interview for every 1.7 hours • Perform 97 dialings per completed interview • 3,200 sample records yield ~100 completed interviews • Bottom Line: We have to call many, many more cell phone numbers before finding someone who will complete the interview


  20. Why Weight? • We weight survey data to make our sample better match the population • Some observations “get counted” more than others

  21. BRFSS Weighting Systems The old BRFSS system used gender, age, race/ethnicity, & region within state to adjust the final results. The new rake weights adds adjustment by education level, marital status, renter/owner status & phone source (landline vs. cell phone) The new “raked” weights should improve the representativeness of the sample, particularly regarding socioeconomic status The new weights, together with adding cell-phone interviews, produces different estimates for some health indicators

  22. Some estimates change a lot: Estimate increases by ~ 5.5 percent

  23. Estimate increases by ~ 3.3 percent

  24. Some estimates change very little: Estimate increases by ~ 1.0 percent

  25. Estimate increases by ~ 0.9 percent

  26. Future developments

  27. Change to Geographic Strata • Beginning in 2014, geographic strata will be based on Area Health Education Center regions • Able to stratify both landline and cell phone samples for these area

  28. We will produce estimates for • State as a whole • Eastern, Piedmont & Western Carolina • AHECS • Counties when possible • At least 500 completed interviews in the sample

  29. How to access results

  30. Data for a calendar year are combined and analyzed • Results for state and sub-regions are posted to SCHS Web page • Main SCHS Web Page • • NC BRFSS Web Page •

  31. Contact Information: James CassellHead of Survey Operations & BRFSS CoordinatorState Center for Health StatisticsNorth Carolina Division of Public Health2422 Mail Service CenterRaleigh, NC 27699-2422Voice: 919-855-4485Fax: 919-715-7899Email: BRFSS Web Page State Center for Health StatisticsDivision of Pubic HealthNC Dept. of Health & Human Services