Household Interview Questionnaires
The following questionnaires are administered by trained interviewers in the participant's home.
- Screener Questionnaire (also referred to as Screener Module 1): administered on the doorstep of the selected household to determine if anyone in the household is eligible to participate in the survey.
- Relationship Questionnaire (also referred to as Screener Module 2): administered in the home to establish the relationship of the household members and thereby determining family "units" (e.g., a married couple, a couple living as married, etc.) within each household.
- Family Questionnaire: administered in the home to obtain family-level information about health insurance coverage, housing characteristics, food security status, and family income, etc.
- Sample Person Questionnaire: to collect individual level information on each participant regarding demographic, socioeconomic, dietary behavior, and health-related history.
Mobile Examination Center (MEC) Questionnaires
During the visit to the examination center additional questions are administered to cover more sensitive topics, such as reproductive health and alcohol use. The MEC interview is conducted in a private setting and consists of the following two questionnaires:
- Computer-Assisted Personal Interview (CAPI) Questionnaire: The first part of the MEC interview uses the CAPI system and is conducted by a trained MEC interviewer.
- Audio-Computer-Assisted Self-Interview (ACASI) Questionnaire: The second part of the MEC interview uses the ACASI system. The ACASI format permits the respondents to hear questions through headphones and to read questions on a computer screen in their choice of language. Participants respond the questions at their own speed using the touch screen. The MEC interviewer will give the participant a brief demonstration of the use of ACASI prior to the start of the interview, but will not be present for this part of interview, instead, he/she will be available nearby should the participant have a question.
Respondent and Proxy Rules
The screener and relationship questionnaires are administered to an adult household member aged at least 18 years or an emancipated minor determined by state-specific criteria. The family questionnaire is completed for every family unit sampled within the household. The respondent for the family questionnaire is typically the head of household and must be an adult family member (aged 18 years or older) or an emancipated minor.
The sample person questionnaire is administered to all participants or their proxies; however, eligibility for each specific questionnaire section is determined by the participant's age and gender. Participants 16 years of age and older and emancipated minors are interviewed directly. An adult proxy provides information for survey participants who are under 16 years of age and for participants who cannot answer the questions themselves.
The MEC interview is administered to participants 8 years of age or older. Eligibility for each specific questionnaire sections is determined by the participant's age (at the time of screening) and gender. In general, the CAPI portion could be administered using a proxy interview or an interpreter if needed. A small number of sections have different respondent rules, please refer to the documentations that accompany the released datasets for section-specific information. Due to the sensitive nature of the questions in the ACASI questionnaire, no proxies or interpreters are used. Therefore, mentally impaired individuals, or participants who are unable to understand English, Spanish, Korean, Vietnamese, or Chinese (traditional/Mandarin, simplified/Mandarin, or traditional/Cantonese) are not eligible.
Questionnaire and Interview Languages
All NHANES questionnaires were translated into Spanish and can be administered in either English or Spanish based on respondent preference. To facilitate the oversampling of the Asian-Americans, which began in 2011, selected survey materials were translated into Mandarin Chinese, both traditional and simplified, Korean, and Vietnamese. Materials translated to these Asian languages included hand cards, glossaries of terms, consents, examination scripts, and informational brochures. All translations were done using the NCHS Research Ethics Review Board (ERB) approved forward translation process. A large percentage of the household interviewers and all MEC interviewers are bilingual in English and Spanish. Interpreters are used for non-English/non-Spanish speaking participants.
In addition to the English and Spanish versions, the 2011-2016 MEC ACASI questionnaire was translated into Chinese (traditional/Mandarin, simplified/Mandarin, and traditional/Cantonese), Korean, and Vietnamese for use with participants 20 years and older when necessary. The respondent chooses their preferred language.
Automated Data Collection
NHANES household interview and MEC interview data are recorded electronically using computerized questionnaire forms. After data collection was completed, the interview data files were transmitted electronically to a central survey database system.
The NHANES automated interview systems have built-in edits and range checks for many question response options. When unusual, inconsistent, or unrealistic responses were recorded, the interviewer was alerted immediately and instructed to verify or edit the initial response. The systems also have online help screens built-in to assist interviewers in defining key terms used in the questionnaires.
All NHANES interviewers completed a comprehensive training program, although many of them had prior interviewing experience. The training included general interviewing techniques, role-playing exercises and practice interviews with live respondents, all of which were monitored by NCHS and contractor staff. In addition to interview administration, interviewers also participated in a series of cultural competency trainings to help them recognize and respect cultural differences.
Interviewer Quality Control Monitoring
Extensive pretesting was completed prior to implementing the questionnaires in the field.
Several types of quality control monitoring procedures were implemented to ensure that high quality data were collected during the survey. Interviewers were frequently accompanied on interviews and observed by field supervisors and NCHS staff to verify that the interviewing protocol was administered correctly. At least 10% of every household interviewer's work (including screening and interview) were randomly selected and validated by field supervisors via phone or field visit shortly after the completion of household data collection. Accuracy and completeness of selected key items (such as age, birth date, gender, spelling of first and last name, address, and future contact references) for all cases were reviewed by field office staff and MEC coordinators throughout the data collection, data retrieval and updates were carried out as needed. In addition, each household and MEC CAPI interview was digitally recorded unless the survey participant specified that he/she did not want the interview recorded (the request for permission and the participant's response to record were recorded). The recorded interviews were reviewed by NCHS staff and interviewer supervisors. Interviewers were retrained on survey procedures when necessary.
NCHS encouraged the interviewers to provide constructive comments and feedback based on their field experiences. NCHS used field staff and interviewer feedback to improve the questionnaires and survey materials. Survey staff debriefing and training sessions were conducted bi-annually. NCHS and contractor staff participated in the debriefing meetings. Interviewers were trained on new survey content and protocol changes prior to implementation in the field.
Data Preparation and Analytic Guidance
During data preparation, variable frequency counts were checked, questionnaire "skip" patterns were verified, the reasonableness of responses to the questions, and interviewer comments were reviewed. Edits were made to some variables to ensure the completeness, consistency, and analytic usefulness of the data. Edits were also made, when necessary, to address data disclosure concerns. The questionnaire section-specific documentations provided with released data files describe the measures taken in greater detail. We strongly encourage that all data users, prior to any analysis of the data, read all relevant documentations on the survey overall and for the specific data files to be used in their analysis. Specific data file documentation can be found via the link next to the respective data file on the NHANES website. Data users should also reference the NHANES Analytic Guidelines prior to beginning any analyses.