A multistage area probability sample for each of the 50
states and the District of Columbia has been used since 1999. A coordinated sample design was developed for the 2005 through 2009 NSDUHs. The 2011 NSDUH is an extension of the 5-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. The 2011 NSDUH continues the 50 percent overlap by retaining half of the second-stage units from 2010. 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 2011 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 2011 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 2011 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 2011 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. Beginning in 2002, 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. In 2011, an oversample was included to help in measuring and reporting on the impact that the April 2010 Deepwater Horizon oil spill had on substance use and mental health along the gulf coast. The target sample was expanded by 2,000 cases in four Gulf Coast States (Alabama, Florida, Louisiana, and Mississippi). The achieved sample size for the 2011 survey was 70,109 persons. The public use file contains 58,397 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.
audio computer-assisted self interview (ACASI)
computer-assisted personal interview (CAPI)
computer-assisted self interview (CASI)
Strategies for ensuring high rates of participation resulted in a weighted screening response rate of 86.98 percent and a weighted interview response rate for the CAI of 74.38 percent. (Note that these response rates reflect the original sample, not the subsampled data file referenced in this document.)