Application Process

Overview

Complete all requests for access to National Center for Health Statistics (NCHS) Research Data Center (RDC) restricted-use data in the Standard Application Process (SAP) portal. Within the SAP portal, please summarize your restricted-use data needs for each section of the application. You must provide a list of all variables needed for your research in a data dictionary and a description of the output needed for your final data product. A data product can be a paper, journal article, or presentation.

Application tips

Tip 1: Create an SAP account that establishes a user ID and password before submitting an application.

Tip 2: The Principal Investigator (PI) 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.

Tip 3: Select the dataset you need from the SAP portal to begin the application. You may select multiple datasets at a single time; however, the requested data must be related to your research question(s).

Tip 4: If any NCHS data are missing from the SAP portal, please send an email to rdca@cdc.gov.

Tip 5: The SAP portal will require you to upload a variety of documents for various sections of the application. NCHS recommends that you prepare these documents in advance for upload at the time you are submitting the application. These documents would include—

• Data dictionary that lists all requested variables needed for research
• Description of research methodology used
• List of references
• Detailed description of requested output that includes table shells
• Timeline for managing the project within a three-year time period

Upload each document into its appropriate section within the application. Do not combine files. The accepted file formats for these documents are .pdf and .docx.

Tip 6: In the agency benefits section, provide a description of how your research benefits public health.

Sample application documents

• Sample SAP application
• Variables requested
• Methodology
• Requested output

Student advisor agreement

When a PI submits an application on behalf of a student, the PI must include a signed RDC Student Advisor Agreement.

The RDC student advisor agreement summarizes RDC policies and procedures that the advisor and student will agree to follow.

Creating a data dictionary

The data dictionary is an essential part of the application. It must list every variable needed for your research project. Upload it into your application. During the application review process, NCHS will use it to assess the disclosure risk of the project. Once NCHS approves the application, it uses the data dictionary to create your dataset.

There are three sections in the data dictionary.

Public-use data

Please list 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 restricted-use data.

Restricted-use data

List the restricted-use variables you need to answer your research question. We list many of the restricted-use variables 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.

Data dictionary guidelines

1. List or provide the following in a table:

• Filename for the data source (e.g., NHIS 2000 person file)
• Year
• Variable names
• Variable descriptions

2. If using variables from a NCHS public-use dataset, provide the variable names given in the public-use file documentation.

3. Highlight the variables in the data dictionary that you want used to merge datasets. It is important to format these variables consistently between datasets for the merge to successfully complete.

Data dictionary considerations

Provide one data dictionary that lists the variables necessary for your research instead of separate ones for public and restricted use for the following surveys—

• National Hospital Discharge Survey
• National Ambulatory Medical Care Survey
• National Hospital Ambulatory Medical Care Survey

Data dictionary examples

Because all data systems are slightly different, the data dictionary may come in a variety of styles.

Sample Data Dictionaries—

• National Health and Nutrition Examination Survey (NHANES)
• National Health Interview Survey (NHIS)
• National Survey of Children's Health (NSCH)
• Data Linkage Activities

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). These changes may affect the disclosure risk and whether the RDC can release your output.

Common types

Change in research team

Your application must be amended if a team member departs the project. You must amend your application if a new member joins your team by providing their contact information. This new person must complete the confidentiality requirements.

Additional variables needed

Adding new variables to your analytic dataset may change the disclosure risk of the research and/or output described in your application. Adding variables requires amending your application and may result in additional costs.

New methods used

There may be a case where your analytic plan changes significantly from the method stated in the approved application. Please discuss methodological changes with your RDC analyst before conducting the new analysis. You will need to document methodological changes in an amended application.

Changes to output

If the content and/or types of output you need changes, then you will need to amend your application. Revise the output description in an amended application. The RDC can only release output to you that has no disclosure risk. The output you generate must match the output described in your approved application.

Amendment timeline

Application amendments require approval; typically, the NCHS RDC takes four weeks to review an amendment. 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.

Project Renewal

All RDC projects expire three years after approval. Researchers who need more time to complete their originally approved project may renew their project for an additional three years. The PI must initiate the project renewal process with their assigned RDC analyst.

Project renewal is only granted once per project, and it incurs a renewal fee. The project will be closed at the end of the three-year renewal period.

To qualify for a project renewal:

• The project database must remain unchanged.
• The research topic cannot be altered.

After project renewal, all amendments will be charged a fee except for changing project team members. See "Amendments" for more information.