appraisal vs dissertation

appraisal

noun
  • A judgment or assessment of the value of something, especially a formal one. 

  • The act or process of developing an opinion of value. 

dissertation

noun
  • A lengthy lecture on a subject; a treatise; a discourse; a sermon. 

  • A formal exposition of a subject, especially a research paper that students write in order to complete the requirements for a doctoral degree in the US and a non-doctoral degree in the UK; a thesis. 

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