experiment vs proofreading

experiment

noun
  • A test under controlled conditions made to either demonstrate a known truth, examine the validity of a hypothesis, or determine the efficacy or likelihood of something previously untried. 

verb
  • To conduct an experiment. 

proofreading

noun
  • The act or process by which a document is proofread. 

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