69International Journal of Methods in Psychiatric Research, Volume 13, Number 2The US National Comorbidity SurveyReplication (NCS-R): design and field proceduresRONALD C. KESSLER,1PATRICIA BERGLUND,2WAI TAT CHIU,1OLGA DEMLER,1STEVENHEERINGA,2EVA HIRIPI,1ROBERT JIN,1BETH-ELLEN PENNELL,2ELLEN E. WALTERS,1ALANZASLAVSKY,1HUI ZHENG11 Department of Health Care Policy, Harvard Medical School, Boston MA, USA2Institute for Social Research, University of Michigan, Ann Arbor MI, USA ABSTRACT The National Comorbidity Survey Replication (NCS-R) is a survey of the prevalence and correlates ofmental disorders in the US that was carried out between February 2001 and April 2003. Interviews were administeredface-to-face in the homes of respondents, who were selected from a nationally representative multi-stage clustered areaprobability sample of households. A total of 9,282 interviews were completed in the main survey and an additional 554short non-response interviews were completed with initial non-respondents. This paper describes the main features ofthe NCS-R design and field procedures, including information on fieldwork organization and procedures, sampledesign, weighting and considerations in the use of design-based versus model-based estimation. Empirical information ispresented on non-response bias, design effect, and the trade-off between bias and efficiency in minimizing total mean-squared error of estimates by trimming weights.Key words: design effects, epidemiologic research design, sample bias, sample weights, survey design efficiency, survey samplingliterature on survey methodology (Groves, Fowler,Couper, Lepkowski, Singer and Tourangeau, in press)and the fourth of which is based on considerationsunique to the NCS-R. First, the coverage propertiesof an area probability sample are superior to othersamples such as those used in telephone, mail, orInternet surveys. Second, the accuracy of screeningand household enumeration procedures, which arerequired to create a probability sample, is greater inface-to-face surveys than in surveys based on theseother modes of data collection. Third, response ratesare generally much higher in face-to-face surveysthan in those based on other modes of data collec-tion. Fourth, the NCS-R interview schedule wasquite long and highly complex, making it impossibleto use these other modes effectively. Although the above four considerations weresufficient to convince us that a face-to-face surveymode was needed, there were also additional advan-tages of this mode that we recognized and used to ouradvantage. One was related to the issue of length andThe current paper presents an overview of theNational Comorbidity Survey Replication (NCS-R)survey design and field procedures. We also discussweighting and design effects. Although the instru-ment used in the NCS-R is described in a separatereport in this issue (Kessler and Üstün, 2004), thereis some discussion of broad outlines of the interview,with implications for the design of the survey.Survey modeThe NCS-R was carried in the homes of a nationallyrepresentative sample of respondents betweenFebruary 2001 and April 2003. The survey wasadministered using laptop computer-assisted personalinterview (CAPI) methods by professional surveyinterviewers employed by the Survey ResearchCenter (SRC) of the Institute for Social Research atthe University of Michigan. The decision to use face-to-face administration rather than telephone, mail,or Internet administration was based on four mainfactors, the first three of which come from the IJMPR 13.2 3rd v4 25/6/04 10:26 am Page 69Kessler, Berglund et al.70complexity of the interview, which can lead to highrespondent burden in some cases. The face-to-facesurvey mode made it possible for interviewers togauge respondent fatigue and to suggest short breaksif respondents needed time to regain their focus.Along the same lines, interviews with respondentswho had complex histories of psychopathology wereoften broken up into two or more sessions that werespread out over a period of days or even weeks. In arelated way, use of the face-to-face mode minimizedthe problem of the respondent prematurely haltingthe interview (which is common in telephoneadministration) or completing only part of the assess-ment (which is common in mail questionnaires andInternet surveys). Break-offs of this sort are rare inin-person surveys. This is especially true when, as in the NCS-R, interviewers are trained to monitorrespondent fatigue and to suggest breaks. Consistentwith this thinking, only 107 out of 9,389 initialNCS-R respondents broke off an interview.The decision to use CAPI rather than paper-and-pencil (PAPI) administration was based on the factthat the interview schedule had many complex skips.These skips create opportunities for interviewer errorin PAPI that are avoided in CAPI due to thecomputer controlling the skip logic. Computer-assisted personal interviews can also be cost-effectivewhen the sample size is large because the investmentin the application programming is less than thelabour needed to keypunch PAPI responses. An addi-tional appeal of CAPI compared to PAPI is that theinterviewer can be prompted for missing or inconsis-tent responses while the interview is in progress,allowing these problems to be resolved immediately.Given the fact that the NCS-R interview askedabout a number of embarrassing feelings and behav-iours, a question could be raised whether the methodof audio computer-assisted self-administered inter-viewing (A-CASI) should have been used instead ofmore conventional CAPI. The use of A-CASI allowsrespondents to enter answers to embarrassing ques-tions into a laptop without the interviewer knowingtheir answers by using digital audio recordings andheadsets connected to the laptop to administer thesurvey questions. There is now impressive evidencesuggesting that A-CASI leads to significantly higherreports of some illegal or embarrassing behaviours(Turner, Lessler and Devore, 1982; Tourangeau andSmith, 1998; Turner, Ku, Rogers, Lindberg, Pleckand Sonenstein, 1998). Our decision not to use A-CASI despite this evidence was based on a concernabout non-comparability of responses for purposes oftrending with the baseline NCS and also with timingconsiderations. Regarding the latter, the field periodfor the NCS-R was set back more than 2 years fromits original start date because of unplanned complexi-ties in mounting a parallel national survey ofadolescent mental health. The