Notes for Data Users

2000 Data Limitations

The BRFSS is a cross-sectional surveillance survey currently involving 52 reporting areas. The Virgin Islands and Guam are point-in-time surveys and are not discussed here. 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 2000 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 question. The following section identifies other known variations for the 2000 data year.

A. 2000 Data Anomalies and Deviations from Sampling Frame and Weighting Protocols

In several states, a portion of sample records intended for use during one month were completed in another month. This deviation will disproportionately affect analyses based on monthly, rather than annual data.

Several states did not collect data for all twelve months of the year. Ohio did not collect data January through March, or July through September. Their data include interviews completed in January and February of 2001. Arizona is missing data in July, August, September and December. The District of Columbia did not start the survey until April.

Hawaii did not release telephone numbers in accordance with protocol and may have introduced bias into the survey. More information about the quality of the survey data can be found in the 2000 BRFSS Summary Data Quality Report.

Telephone coverage varies by state and also by subpopulation. Telephone coverage averages about 95% for U.S. states as a whole, but ranges from 1.8% non coverage in Delaware, to 13.3% in New Mexico. It is estimated 10% of households in Puerto Rico are without telephones.

Dual questionnaires and/or partial year coverage occurred in Illinois. Illinois used a dual questionnaire and collected data on core items involving immunization, cholesterol, hypertension, colorectal screening, injury and alcohol consumption and modules concerning exercise, cigar smoking, fruits and vegetables and weight control for only six months of the interviewing period.

California modified the wording of mammography, clinical breast exam, and Papanicolaou (PAP) smear questions. More than 7%, (n=309) of Puerto Rico's respondents did not answer the fruit and vegetable questions. These questions may have limited comparability to those of other reporting areas.

More information about survey item non-response can be found in the 2000 BRFSS Summary Data Quality Report.

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This page last reviewed June 22, 2005

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Centers for Disease Control and Prevention
National Center for Chronic Disease Prevention and Health Promotion
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