uncertainty vs variability

uncertainty

noun
  • A parameter that measures the dispersion of a range of measured values. 

  • Doubt; the condition of being uncertain or without conviction. 

  • Something uncertain or ambiguous. 

variability

noun
  • The degree to which a thing is variable. In data or statistics this is often a measurement of distance from the mean or a description of data range. 

  • The state or characteristic of being variable. 

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