The Collaborative International Dictionary of English v.0.48:

Biostatistics \Bi`o*sta*tis"tics\, n. [Gr. bi`os life + E.
   statistics.] (Biol.)
   Vital statistics.
   [1913 Webster]

WordNet (r) 3.0 (2006):

biostatistics
    n 1: a branch of biology that studies biological phenomena and
         observations by means of statistical analysis [syn:
         biometrics, biometry, biostatistics]