Behavioral Risk Factor Survey Module
Technical Notes
Wisconsin Behavioral Risk Factor Survey (BRFS)
The Wisconsin BRFS Program is located in the Bureau of Health Information
and Policy (BHIP), Division of Public Health, Wisconsin Department of
Health Services. BRFS is managed by the Wisconsin BRFS
coordinator/program director in conjunction with the Centers for Disease
Control and Prevention (CDC).
Sample Design
The BRFS is designed to represent the adult (age 18+) population living in
Wisconsin households. The sample contains a number of strata that varies from
year to year. At a minimum, the strata correspond to the five Department of
Health Services (DHS) regions, with additional strata consisting
of large counties and oversamples of specific populations such as African
Americans and Hispanics/Latinos.
BRFS sampling excludes adults living in institutions and other group quarters
and those living in households without landline telephones. (BRFS currently
excludes adults living in households with only a cell phone, but may include
them in the near future.)
In general, the BRFS sample is selected in two stages. Within each stratum,
telephone numbers are generated using random procedures. One adult is
randomly selected in each eligible household. The Centers for Disease Control
and Prevention (CDC) specifies that a new sample is opened and closed each
month. Thus, the BRFS consists of 12 separate monthly samples combined to
make the annual data set for purposes of weighting and analysis.
Recommendations for Analysis and Reporting of Results
Use of confidence intervals around BRFS survey estimates is strongly
recommended. The Bureau of Health Information and Policy recommends
basing all reported estimates on a minimum of 100 interviews; closer to 400
interviews is optimal.
Analysis of sub-groups (e.g., women of childbearing age) requires
consideration of issues concerning adequate sample size and appropriate
population estimates.
If results are based on more than one year of data, users should divide the
"Estimated Number in Population" by the number of years. This will produce
an average population estimate for the time period.
For example, selecting General Health Status for 2003-2005 shows an
"Estimated Number in Population" of 7,198,600 who were in excellent/very
good health in Wisconsin. Dividing this result by the number of years (3)
yields 2,399,533.33, which rounds to 2,399,500. During 2003-2005 there were
approximately 2,399,500 adults in excellent/very good health in Wisconsin.
Weighting
Each interview is weighted to adjust for the sample design and to remove bias.
When the appropriate weight is applied to each interview record, BRFS data
are representative of the total non-institutionalized Wisconsin adult population
(ages 18+) living in households with landline telephones.
The weights:
-
Correct for differences in the probability of selection due to nonresponse
and non-coverage errors.
-
Adjust for distribution differences – by age, race and gender – between
the sample and the Wisconsin adult population.
-
Allow the generalization of findings to the entire Wisconsin adult
population, not just to those who respond to the survey.
Measures
The measures included in the WISH Behavioral Risk Factor Survey module are
those for which data is available from all survey years.
RETURN to previous page
Last Revised: September 09, 2009
| 
