Notes for Data Users

2001 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 2001 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 2001 data year.

A. 2001 Data Anomalies and Deviations from Sampling Frame and Weighting Protocols

In several states, a portion of sample records intended for use during one month was 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 12 months of the year or completed interviews in calendar year 2002. Florida, Hawaii, and Texas did not report any interviews in January. New Jersey and the U.S. Virgin Islands did not complete any interviews in January or February. The District of Columbia did not complete any interviews in January, February, or March. Nevada completed 302 interviews in January or February 2002. Illinois, New Mexico, South Dakota, and Wisconsin had small numbers of completed interviews in January, 2002.

More information about the quality of the survey data can be found in the 2001 BRFSS Summary Data Quality Report.

Telephone coverage (households with telephones) varies by state and also by sub-population. Telephone coverage averages 94.5% for U.S. states as a whole, but ranges from 1.8% noncoverage in Delaware, to 13.3% in New Mexico. It is estimated that 10% of households in Puerto Rico are without telephones.

More information about telephone coverage can be found in the 2001 BRFSS Summary Data Quality Report.

Illinois
Illinois used a dual questionnaire and collected data on core items involving immunization, cholesterol awareness, hypertension awareness, arthritis, firearms, disability, physical activity, prostate cancer screening, colorectal cancer screening, and HIV/AIDS knowledge and prevention, and a module on fruit and vegetable consumption on approximately half of respondents. Fruit and vegetable consumption questions were not asked in August but were asked of all respondents in December. Questions on hypertension awareness, cholesterol awareness, arthritis, immunization, firearms, disability, physical activity, prostate cancer screening, colorectal cancer screening, and HIV/AIDS knowledge and prevention were asked of all eligible respondents in August.

California
California modified the wording of the health plan, diabetes, and the frequency of alcohol consumption questions. These questions may have limited comparability to those of other reporting areas. Several states that used the Tobacco Indicators module inappropriately skipped question 6 (HOUSESMK) in the module for part of the year. The HOUSESMK field was left blank in these states if the question was not asked. The Tobacco Indicators module has a second problem where several states skipped question 4 (GETCARE ) when question 3 (LASTSMK) had a response of 1, 2, 3, or 4. In some states the affected records were coded, 9 Refused, even though the respondents were not asked the questions, other states left the field blank.

The number of affected records by state and months for question 6, HOUSESMK are

The number of affected records by state and months for question 4, GETCARE are

More information about survey item nonresponse can be found in the 2001 BRFSS Summary Data Quality Report.

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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