reliability vs validity

reliability

noun
  • the ability to measure the same thing consistently (of a measurement indicating the degree to which the measure is consistent); that is, repeated measurements would give the same result (See also validity). 

  • The quality of being reliable, dependable, or trustworthy. 

  • measurable time of work before failure 

validity

noun
  • A quality of a measurement indicating the degree to which the measure reflects the underlying construct, that is, whether it measures what it purports to measure (see reliability). 

  • The genuinity - as distinguished from the efficacity or the regularity - of a sacrament as a result of some formal dispositions being fulfilled. 

  • The state of being valid, authentic or genuine. 

  • State of having legal force. 

How often have the words reliability and validity occurred in a corpus of books? (source: Google Ngram Viewer )