Application Process

Standard Application Process
All requests for access to NCHS restricted-use data must be completed in the Standard Application Process (SAP) portal.  Within the SAP portal, please summarize your restricted-use data needs for each section of the application. As part of your application, for example, you must provide a data dictionary and a description of the output you need for your final data product (e.g., paper, journal article or presentation).

Standard Application Process portal 

Tips for Submitting the Application:
    1. You must create an SAP account to obtain a user ID and password prior to submitting an application.
    2. The Principal Investigator will receive all notifications about the progress of application review and status. This will be the only account authorized to edit, submit, or withdraw the application.
    3. You must select the dataset you need from the metadata to begin the application. You may select multiple datasets at a single time; however, the requested data must address the same research question(s).
    4. Consider all the data needed for analysis before you start the application.  If you find you need to add or remove data, you must submit a new application.
    5. If any NCHS data are missing from the metadata, please send an email to
    6. The SAP will require you to upload a variety of documents for various section of the application. It is recommended that you prepare these documents in advance for upload at the time you are submitting the application.  These documents would include a data dictionary of requested variables, a description of research methodology used, a list of references, a detailed description of requested output, and a timeline for managing the project within a three-year time period. Each document should be uploaded into its appropriate section within the application. Do not combine files.  The accepted file formats for these documents are  .pdf and .docx.
    7. In the Agency Benefits section, provide a description of how your research benefits public health.

      Sample Application
      SAP Application [PDF - 164 KB]

      Variables Requested [PDF - 62 KB]
      Methodology [PDF - 66 KB]
      Requested Output [PDF - 61 KB]
Student Advisor Agreement

If a Principal Investigator (PI) is submitting the application on behalf of a student, the PI must upload a signed RDC Student Advisor agreement with the application. The RDC Student Advisor agreement summarizes RDC policies and procedures  that the Advisor and student will agree to follow.

Student-Advisor Agreement [PDF – 121 KB]

Creating the Data Dictionary

The data dictionary is an essential part of the application. It is uploaded into your application. During the application review process, it is used to assess the disclosure risk of the project. Once the application is approved, the data dictionary is used to create your dataset.

There are three sections to the data dictionary:

  • Public-use Data – Please select only the variables from the public-use data that are necessary to answer your research question. We will not merge the entire public-use file to your dataset.
  • Restricted-use Data – Many of the restricted-use variables are listed on our Restricted Data page, however these lists are not exhaustive. Reviewing the survey documentation (i.e., questionnaire) will help you determine what additional variables may be available.
  • Non-NCHS Data – If you wish to have variables added from another data source, please provide a list of those variables. Do not exceed 100 variables.
General Guidelines for Data Dictionary
  1. List or provide in a table the following information:
    • Filename of where the data are coming from (e.g. NHIS 2000 person file)
    • Variable Names
    • Variable Descriptions
  2. If using variables from a NCHS public-use dataset, provide the variable names that are given in the public-use file documentation.
  3. Highlight the variables in the data dictionary that will be used to merge datasets. It is important that these variables be formatted consistently between datasets for the merge to successfully complete.
Data Dictionary Examples

Because all data systems are slightly different, the data dictionary may come in a variety of styles. Please see the various examples for the data systems.

Sample Data Dictionary, National Health and Nutrition Examination Survey (NHANES)[PDF – 17 KB]

Sample Data Dictionary, National Health Interview Survey (NHIS [PDF – 196 KB]

Sample Data Dictionary, National Survey of Children’s Health (NSCH)[PDF – 15 KB]

Sample Data Dictionary, Data Linkage Activities [PDF – 75 KB]

    • NHDS, NAMCS, and NHAMCS users:  Instead of providing a public-use and restricted-use data dictionary, please provide one data dictionary that chooses the variables necessary for your research.
Application Amendments

We understand that research evolves and may change from the day you submit your application. NCHS must approve project changes, also known as amendments, for these changes may affect the disclosure risk and whether your output may be released.

Common Amendment Types

Change in Research Team:

    • The application must be updated to include the new team member contact information and this new person must complete the confidentiality requirements.

Additional variables needed:

    • Adding variables may change the disclosure risk of the research and/or output described in your application
    • Adding variables may result in additional costs

New methods used or additional types of output needed:

    • If the analytic plan changes significantly from the method stated in the approved application, please discuss the changes with your RDC Analyst before conducting the analysis. Changes will need to be documented in the application.
    • If the content and/or types of output need to change, your application will need to be amended.  You will need to revise the description of output in an amended application.  The RDC can only release output to you that has no disclosure risk and the output released  must match the description in your approved application.

Application Amendments require approval; typically, approvals are given within four weeks. However, a full review of 8–12 weeks may be necessary for more complex amendments.

Contact your assigned RDC analyst for instruction on how to amend your application.