In the context of federal funding from agencies such as the NIH or the NSF, the PI is the person who takes direct responsibility for completion of a funded project, directing the research and reporting directly to the funding agency. For small projects that incorporate 1-5 people the PI is typically the person who conceived of the investigation, but for larger projects the PI may be selected by a team to obtain the best strategic advantage for the project.
In the context of a clinical trial a PI may be an academic working with grants from NIH or other funding agencies, or may be effectively a contractor for a pharmaceutical company working on testing the safety and efficacy of new medicines.
Certification for principal investigator
The Association of Clinical Research Professionals (ACRP) provides a certification, specific to physician investigators and principal investigators. ACRP offers the designation "Certified Physician Investigator (CPI)".
Additional training and support tools for a PI exist in the form of the Principal Investigators Association. A not-for-profit corporation, "PIA communicates and promotes best practices and continuing professional education for garnering financial support" while also encouraging proper use of "monetary, material, and personnel resources."
- "NSF Grant Policy Manual, 210f, "Definitions: Principal Investigator"". National Science Foundation. July 2002. https://www.nsf.gov/pubs/2002/nsf02151/gpm2.jsp#210. Retrieved 10 January 2022.
- "NIAID Glossary of Funding and Policy Terms and Acronyms". National Institute of Allergy and Infectious Diseases. 18 April 2011. Archived from the original on 10 January 2011. https://web.archive.org/web/20110110185220/http://funding.niaid.nih.gov/researchfunding/glossary/pages/p.aspx. Retrieved 10 January 2022.
- "Association of Clinical Research Professionals - Certification". Association of Clinical Research Professionals. https://acrpnet.org/certifications/. Retrieved 10 January 2022.
- "Principal Investigators Association Mission". Principal Investigators Association. https://www.principalinvestigators.org/our-mission/. Retrieved 10 January 2022.