Data is commonly defined as "facts or information which serve as the basis for decisionmaking, discussion and reasoning, or calculation."
When a grant is funded by the NIH, "any and all data collected as part of that funded project are owned by the university (commonly called the grantee institution)." Thus, all of the data generated as part of an NIH funded research project are the property of the university. This includes the research notebooks, computer files, etc of everyone working on the project. The notebooks and data may not be taken from the lab without official permission.
Many universities delegate the responsibility for the data to the principal investigator. In such cases, upon agreement with the principle investigator, a trainee may be allowed to take reproductions of original data or research notebooks upon leaving the project.
Source: Macrina, F. 1995. Scientific integrity. American Society for Microbiology, Washington, D.C.