WordNet (r) 3.0 (2006):

predictability
    n 1: the quality of being predictable [ant: unpredictability]

Moby Thesaurus II by Grady Ward, 1.0:

37 Moby Thesaurus words for "predictability":
   authenticity, authoritativeness, calculability, dependability,
   divinability, faithworthiness, firmness, foreknowableness,
   foreseeability, foretellableness, frequency curve,
   frequency distribution, game theory, invincibility,
   mathematical probability, operations research, probability theory,
   probable error, quantum mechanics, reliability, secureness,
   security, solidity, soundness, stability, standard deviation,
   statistical mechanics, statistical probability, statistics,
   staunchness, steadfastness, steadiness, substantiality,
   trustworthiness, uncertainty principle, unerringness, validity