decide vs step in

decide

verb
  • to resolve (a contest, problem, dispute, etc.); to choose, determine, or settle 

  • to make a judgment, especially after deliberation 

  • to cause someone to come to a decision 

step in

verb
  • To get involved; to act 

  • To act as a replacement or substitute. 

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