Source : Webster's Revised Unabridged Dictionary (1913)

Probative \Pro"ba*tive\, a. [L. probativus: cf. F. probatif.]
   Serving for trial or proof; probationary; as, probative
   judgments; probative evidence. --South.

Source : WordNet®

probative
     adj : tending to prove a particular proposition or to persuade you
           of the truth of an allegation