Skip Navigation Links
Centers for Disease Control and Prevention
 CDC Home Search Health Topics A-Z

National Center for Chronic Disease Prevention and Health Promotion
Behavioral Risk Factor Surveillance System

BRFSS Home | Contact Us



BRFSS Contents


Item: Prevalence Data
Item: SMART: City and County Data
Item: BRFSS Maps
Item: Web Enabled Analysis Tool (WEAT)
Item: Trends Data
Item: Chronic Disease Indicators (CDI)
Item: About the BRFSS
Item: BRFSS Datasets (downloads and documentation)
Item: Chronic Disease and the Environment
Item: Questionnaires
Item: FAQs
Item: State Information
Item: Publications and Research
Item: Training
Item: Site Map
Item: Related Links







Notes for Data Users

2002 Data Limitations

The BRFSS is a cross-sectional surveillance survey currently involving 54 reporting areas. It is important to note that any survey will have natural variation over sample sites; therefore, some variation between states is to be expected. The complex sample design and the multiple reporting areas complicate the analysis of the BRFSS. Although CDC works with the states to minimize deviations, in 2002 there were some deviations in sampling and weighting protocols, sample size, response rates, and collection or processing procedures. In addition, California’s questionnaire had a few minor differences in wording of questions. The following section identifies other known variations for the 2002 data year.

A. 2002 Data Anomalies and Deviations from Sampling Frame and Weighting Protocols

In 75% of the states, a portion of sample records intended for use during one month took more than one month to complete, in some instances, several states used their monthly sample into several months. This deviation will disproportionately affect analyses based on monthly, rather than annual data.

Several states did not collect data for all 12 months of the year or completed interviews in calendar year 2003. Massachusetts and Puerto Rico did not report any interviews in January. The U.S. Virgin Islands did not complete any interviews in January or February. New Jersey did not complete any interviews in January, June, July, August, and September. Nevada completed over 800 interviews in January and February 2003. Alabama, Arkansas, Colorado, Idaho, Illinois, Indiana, Kentucky, North Dakota, New Mexico, New York, Oklahoma, Oregon, Pennsylvania, South Carolina, Texas, Utah, Virginia, the U.S. Virgin Islands, and Wyoming had some completed interviews in January 2003.

More information about the quality of the survey data can be found in the 2002 BRFSS Summary Data Quality Report.







B. Other 2002 limitations of the data

Telephone coverage (households with telephones) varies by state and also by sub-population. Telephone coverage averages 97.6% for U.S. states as a whole, but ranges from 1.1% noncoverage in Connecticut and New Hampshire, to 6.6% in Mississippi. It is estimated that 23.8% of households in Puerto Rico are without telephone service. Data on telephone coverage in United States households are available at http://factfinder.census.gov.

Pennsylvania
Pennsylvania asked all survey respondents the core questions on the 2002 survey, but five different sets of modules were asked based on the residence of the survey respondents. Individuals in Armstrong, Franklin, Chester, and Lancaster counties were all asked different sets of modules and the remaining state residents were asked a different set of module questions. This resulted in five different questionnaires being implemented in Pennsylvania and all module data collected was moved to the state-added questions section. Illinois used a dual questionnaire and collected data on core items involving health status, health care access, exercise, asthma, diabetes, immunization, tobacco use, prostate cancer screening, colorectal cancer screening, and HIV/AIDS knowledge and prevention, and demographics from all eligible respondents. The alcohol consumption core question on drinking and driving (variable DRINKDRI) was asked of about half the respondents while the rest of the questions (ALCDAY3, AVEDRNK, and DRNK2GE5) were asked of all respondents. For the firearms core questions, question 1 (FIREARM4) was asked to all respondents, while questions 2 and 3 (GUNLOAD and LOADULK2) were asked on only half of the respondents. Fruit and vegetable consumption, oral health, seat belt use, family planning, and women’s health questions were asked of about half of eligible respondents. Modules on hypertension awareness, cholesterol awareness, physical activity, healthy days, and childhood asthma were asked of approximately half of all eligible respondents.

California
California modified the wording of the following core questions: firearms, health plan, diabetes, the frequency of alcohol consumption, Hispanic ethnicity question, level of education, and household income questions. The data from the firearms questions are not included in the data set. In addition, California used different age cut-offs for the colorectal cancer screening questions. These questions may have limited comparability to those of other reporting areas.

Other states
Some states had a problem with skip patterns in the Health Care Access section of the Core Survey. For January and part of February for some states, because of CATI programming issues, question 4 (MEDCARE) and question 5 (MEDREAS) had the same variable name. This produced a potential error in the data if someone answered the MEDCARE question “1. Yes” to MEDCARE and then answered 2, 7, or 9 to MEDREAS, their results were overwritten and may have been lost. Several states did call individuals a second time to clarify the MEDCARE and MEDREAS variable values. There were several issues in regards to the new disposition codes that were implemented this year, especially the new code for partial completes (coded 120) and completed interviews (coded 110). In the past, interviews terminated during or after the demographics section would have been coded as a complete interview and the remaining questions unanswered would be coded as refused by the interviewer. For 2002 states handled partial complete interviews differently; they were generally handled in one of three ways: 1) answered the remaining questions as refused and coded the record a 110 Complete, 2) answered the remaining questions as refused and coded the record a 120 Partial complete, or 3) did not ask the remaining questions (answers left as missing) and coded the record a 120 Partial complete. The differences in how the interviews are dispositioned and where in the survey the interview was terminated will have an impact on refusal rates for certain questions/modules and will also affect numbers of completes and partial completes. This will vary state to state. These factors should be taken into account when determining which records to include in any analyses. Changes are being made in 2003 to further clarify the difference between partial completes and complete interviews using just disposition codes.

Several states continue to ask the Diabetes module questions directly after the diabetes questions in the core of the survey, in addition several states ask the Adult Asthma module questions after the asthma questions in the core. Some states have also asked the Childhood Asthma module questions in the demographics section of the core survey after question 6 (CHILDREN) — number of children under age 18 in household. There were a few states that asked the Childhood Asthma module questions of respondents that answered “Refused” to the demographics question assessing the number children in the household. Most states collecting module asked the questions only of respondents indicating there were children in the household.

More information about survey item nonresponse can be found in the 2002 BRFSS Summary Data Quality Report and in the respective states’ Data Quality Reports.

Notes for Data Users library

 2002 | 2001 | 2000 | 1999 | 1998 | 1997 | 1996






Policies and Regulations | BRFSS Home | Contact Us

CDC Home
| Search | Health Topics A-Z

This page last reviewed June 22, 2005

United States Department of Health and Human Services
Centers for Disease Control and Prevention
National Center for Chronic Disease Prevention and Health Promotion
Division of Adult and Community Health