Questionnaire Dwelling Unit-Level and Person Pair-Level Sampling ...

1. Introduction
Traditionally, most household surveys have been designed either to measure
characteristics of the entire household or to focus on a randomly selected respondent from among
those determined to be eligible for the survey. Selecting more than one person from the same
household is considered ill advised since persons from the same household tend to repeat the
same general information characteristic of the entire household. Selecting only one person per
household avoids the clustering effect on the variance. The "one person per household" sampling
approach, however, precludes the opportunity to gather information about the relationships
among household members. In the National Survey on Drug Use and Health (NSDUH), 2 we
allow for a richer analytic capability of a survey designed to ensure a positive pairwise
probability of selection among all eligible household members in each sample household.
Achieving positive probabilities for all pairs within sampled households permits unbiased
estimation of the within-dwelling-unit component of variance. Besides providing efficient data
collection, this sampling method also facilitates the study of the relationships of social behaviors
among members of the same household. This report documents the methodology and
development of calibrated weights for the second objective, the study of behavioral relationships
among persons residing in the same household. The report also describes the development of
questionnaire dwelling unit (QDU) weights, which are of independent interest for studying
household-level characteristics and also are needed for producing household count estimates of
the number of persons belonging to pair relationship domains for use as poststratification
controls for pair weights.
NSDUH allows for estimating characteristics at the person level, pair level, and
household or QDU level. This report describes the weight calibration methods used for the pairand
QDU-level respondents. As described in the person-level report, NSDUH is an annual
survey of about 70,000 persons selected from the civilian noninstitutional population aged 12 or
older from all 50 States and the District of Columbia. Based on a composite size measure, States
were geographically partitioned into roughly equal-sized regions according to population. The
smaller States were partitioned into 12 State sampling (SS) regions, whereas the eight large
States were divided into 48 SS regions. Therefore, the partitioning of the United States resulted
in the formation of a total of 900 SS regions. Under a stratified design with States serving as the
primary strata and SS regions serving as the secondary strata, census tracts, segments, and
dwelling units (DUs) for the screener questionnaire were selected using probability proportional
to size sampling in two stages. A large number of screener dwelling units (SDUs, about 200,000)
were selected to ensure that various age groups (five in all: 12 to 17, 18 to 25, 26 to 34, 35 to 49,
and 50+) of eligible individuals were represented adequately in the final sample. Information
collected from SDUs also provided estimates of population controls (as in two-phase sampling)
for calibration at levels (such as pair and QDU) for which suitable U.S. Bureau of the Censusbased
controls were not available. From each selected SDU, zero, one, or two persons were
selected using a modification of Brewer's method such that prescribed sampling rates for the five
age groups by each State were achieved with high selection rates for youths (12 to 17) and young
adults (18 to 25). Table 1.1 shows the eligible number of selected and responding SDUs, QDUs,
2 This report presents information from the 2006 National Survey on Drug Use and Health (NSDUH). Prior
to 2002, the survey was called the National Household Survey on Drug Abuse (NHSDA).
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