Source : Webster's Revised Unabridged Dictionary (1913)

Conclusiveness \Con*clu"sive*ness\, n.
   The quality of being conclusive; decisiveness.

Source : WordNet®

conclusiveness
     n : the quality of being final or definitely settled; "the
         finality of death" [syn: {finality}, {decisiveness}]
         [ant: {inconclusiveness}]