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

pairs, and persons for each of the 5 years (2002–2006). The distribution of pair data for different
pairs of age groups may vary considerably (see Chapter 2 for details). It is seen that for certain
age group domains, the realized sample size may not be sufficient to yield reliable estimates.
Also, there may be problems of extreme weights due to small pair selection probabilities under
Brewer's method that may cause instability of estimates. These and some other estimation issues
related to pair data are discussed below, along with some solutions that were adopted.
Table 1.1 2002–2006 NSDUH Sample Sizes
Sample Unit 2002 2003 2004 2005 2006
SDU Selected 150,162 143,485 142,612 146,912 151,288
Completed 136,349 130,602 130,130 134,055 137,057
QDU Selected 55,686 56,184 56,251 57,243 58,257
Completed 48,088 47,753 47,651 47,893 47,909
Pair Selected 24,895 25,447 25,722 26,562 26,777
Completed 20,038 20,031 20,109 20,415 19,893
Person Selected 80,581 81,631 81,973 83,805 85,034
Completed 68,126 67,784 67,760 68,308 67,802
First, we note that for studying drug-related behavioral relationships among members of
the same household, pair data is required because the outcome variable generally is defined with
respect to the specific other member selected from the household. However, the parameter of
interest is generally at the person level and is not at the pair level. For example, in the parentchild
pairs, one may be interested in the proportion of children that have used drugs in the past
year who have parents that report talking to their child about drugs. Here the target population
consists only of children, and not all possible pairs. Note that the pair-level (two persons per
QDU) sample forms a subsample of the larger person-level (one or two persons per QDU)
sample, with the QDUs themselves selected from the larger sample of SDUs. NSDUH has
features of a two-phase design, which turns out to be useful for estimating calibration controls
for poststratification of household-level weights and person pair-level weights. No other outside
source is available for obtaining these controls. For this purpose, the screener-level household
weights are poststratified to person-level census counts to obtain more efficient estimated
controls for pair and household data.
In estimation for pair domains, two major problems arise: one is that of multiplicities
because, for a given domain defined by the pair relationship, when the parameter of interest is at
the person level, several pairs in the household could be associated with the same person. The
other problem is that of extreme weights that may arise due to small selection probabilities for
certain pair age groups, which may lead to unstable estimates. Each of these issues is discussed
in turn.
If several pairs in the household are associated with the same person, it is necessary to
use the average measure of behavior relationships for each member, which gives rise to
multiplicities. Thus, the pair weights need to be divided by the person-level multiplicity factors
for each domain of interest, and, therefore, multiplicity factors need to be produced along with
the final set of calibrated weights. Because it is not straightforward to create these multiplicities,
analyses would have to be necessarily limited to pair relationships where the multiplicities were
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