fact-finding vs investigation

fact-finding

noun
  • The determination of factual information. 

adj
  • Designed to determine factual information; investigative. 

investigation

noun
  • The act of investigating; the process of inquiring into or following up; research, especially patient or thorough inquiry or examination 

How often have the words fact-finding and investigation occurred in a corpus of books? (source: Google Ngram Viewer )