as in vs for a fact

as in

adv

  • Used other than figuratively or idiomatically: see as, in. 

  • In the sense of. 

for a fact

adv

  • Used other than figuratively or idiomatically: see for, a, fact. 

  • Without doubt. 

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