Child and Adolescent Functioning and Disability FAQ
- What type of information is in the catalog?
- What age range is covered by the measures in the catalog?
- What types of questions or scales are included as measures of "functioning and disability"?
- Why isn’t all the information collected in NCHS surveys available in public use files?
- What is the Research Data Center (RDC)?
- Are there special conditions for the use of questions or scales appearing in NCHS surveys?
- Where can I find the frequency distribution of responses for a particular measure?
- Why do some measures appear in more than one survey?
- What factors should be considered when an analysis uses data from more than one survey?
- Why are there so many NHANES data files?
- Where can I find more answers to frequently asked questions?
The NCHS Measures Catalog includes information about survey measures including the wording of survey questions, response options, data collection method, and other information. This type of information about survey measures is often called “metadata”. The catalog also includes links to sites with the survey questionnaire, data file, data file documentation, and other relevant information. For some measures, there are links to interactive websites that allow users to tabulate data.
It varies by measure. Each measure includes information about the age range covered by the specific survey question or scale. The term, “children,” is sometimes used in the catalog to refer to all persons less than 18 years of age.
“Functioning and Disability” is a broadly defined topic that includes several aspects of disability: impairments in body functions and structure, limitations in activities and participation, physical and mental health conditions often associated with limitations in activities and participation, the use of assistive technology, health care and educational service use, and health insurance coverage.
Some information, including data on alcohol and drug use, and data collected by the Diagnostic Interview Schedule for Children (DISC), and the DISC Predictive Scale – Youth Conduct Disorder, is not available in publicly released files. These files have not been released in order to preserve privacy and confidentiality, consistent with the confidentiality provisions under which the data were collected. Data files including this sensitive information are made available at the NCHS Research Data Center.
The NCHS Research Data Center (RDC), located at the NCHS headquarters in Hyattsville, MD, allows researchers, meeting certain qualifications and under strict surveillance, to access confidential statistical micro data files. To qualify, researchers must submit a proposal for review and approval. Researchers can use one of three access methods: (1) direct on-site access; (2) remote program submission; or (3) use of programming services provided by RDC staff.
Except where it is noted, material in the NCHS catalog is in the public domain and may be used and reprinted without special permission; citation as to source, however, is appreciated. When permission from the copyright holders to reproduce particular survey questions has been obtained, this is noted in the “Additional information” section of the Measures Summary. In the case of other measures, special conditions for use are also noted in the “Additional information” section of the Measures Summary.
For most measures, the frequency distribution of responses is available in the file that contains documentation for the survey. This file can be accessed by clicking on the link shown in the field for “Data file documentation” in Part 2 of the Measures Summary. In a few cases, public use data files for the survey measure are not available and the documentation for these surveys may not include frequency distributions of responses.
NCHS surveys vary considerably in their content. Using the same measure of a specific mental disorder in several surveys makes it possible to look at a wider range of risk factors and outcomes for the disorder.
For a few measures, data from more than one survey are available. Before combining information from different surveys, researchers should consider the comparability of the data. Some factors that might be considered include differences in the wording of the survey question, response categories, respondent (e.g., proxy respondent for child or self report by child), mode of the survey (e.g., in-person household interview, telephone interview, etc.), context for a survey question (i.e., the other items in the survey questionnaire and placement of a particular survey question in the survey questionnaire), and timing of the survey. Researchers comparing data from a single survey collected during different time periods also need to consider a similar set of factors affecting the comparability of the data.
The data files have been separated to reduce the amount of time needed to download data and documentation from the Internet. The use of many files also makes it easier to produce, edit, and validate data files. Because data from NHANES are presented in many files, the user must often merge files together for a particular analysis. Please refer to the following SAS code example to learn how to merge files together: NHANES data merge code example Cdc-txt[TXT – 2 KB].
For most surveys, go to the home pages of the survey for more information. For NHANES surveys, frequently asked questions are included with each NHANES data release.