A multistage area probability sample for each of the 50
states and the District of Columbia was used since 1999. The 2005 NSDUH is the
first survey in a coordinated five-year sample design. Although there
is no overlap with the 1999-2004 samples, the coordinated design for
2005 through 2009 facilitated a 50 percent overlap in second-stage
units (area segments [see below]) between each two successive years
from 2005 through 2009. This design was intended to increase
precision of estimates in year-to-year trend analyses because of the
expected positive correlation resulting from the overlapping sample
between successive survey years. The 2006 design allows for
computation of estimates by state in all 50 states plus the District
of Columbia. States may therefore be viewed as the first level of
stratification as well as a reporting variable. Eight states, referred
to as the large sample states, had a sample designed to yield 3,600
respondents per state for the 2006 survey. This sample size was
considered adequate to support direct state estimates. The remaining
43 states (which include the District of Columbia) had a sample
designed to yield 900 respondents per state in the 2006 survey. In
these 43 states, adequate data were available to support reliable
state estimates based on SAE methodology. Within each state, sampling
strata called state sampling (SS) regions were formed. Based on a
composite size measure, states were partitioned geographically into
roughly equal-sized regions. In other words, regions were formed such
that each area yielded, in expectation, roughly the same number of
interviews during each data collection period. The eight large sample
states were divided into 48 SS regions each. The remaining states were
divided into 12 SS regions each. Therefore, the partitioning of the
United States resulted in the formation of a total of 900 SS
regions. Unlike the 1999 through 2004 surveys, the first stage of
selection for the 2005 through 2009 NSDUHs was Census tracts. The
first stage of selection began with the construction of an area sample
frame that contained one record for each Census tract in the United
States. If necessary, Census tracts were aggregated within SS regions
until each tract had, at a minimum, 150 dwelling units in urban areas
and 100 dwelling units in rural areas. These Census tracts served as
the primary sampling units (PSUs) for the coordinated five-year
sample. One area segment (one or more Census blocks) was selected within each sampled Census tract. In advance of the survey period, specially trained listers had
visited each area segment and listed all addresses for housing units
and eligible group quarters units in a prescribed order. Systematic
sampling was used to select the allocated sample of addresses from
each segment. Each respondent who completed a full interview was given
a $30 cash payment as a token of appreciation for his or her time. To
improve the precision of the estimates, the sample allocation process
targeted five age groups: 12 to 17 years, 18 to 25 years, 26 to 34
years, 35 to 49 years, and 50 years or older. The size measures used
in selecting the area segments were coordinated with the dwelling unit
and person selection process so that a nearly self-weighting sample
could be achieved in each of the five age groups. The achieved sample
size for the 2006 survey was 67,491 persons. The public use file
contains 55,279 records due to a subsampling step used in the
disclosure protection procedures. A key step in the data processing
procedures established the minimum item response requirements in order
for cases to be retained for weighting and further analysis (i.e.,
"usable" cases). These requirements, as well as full sampling
methodology, are detailed in the codebook.
The civilian, noninstitutionalized population of the
United States aged 12 and older, including residents of
noninstitutional group quarters such as college dormitories, group
homes, shelters, rooming houses, and civilians dwelling on military
installations.
individual
survey data
audio computer-assisted self interview (ACASI)
computer-assisted personal interview (CAPI)
Strategies for ensuring high rates of participation
resulted in a weighted screening response rate of 90 percent and a
weighted interview response rate for the CAI of 74 percent. (Note that
these response rates reflect the original sample, not the subsampled
data file referenced in this document.)