The Collaborative International Dictionary of English v.0.48:

Statistician \Stat`is*ti"cian\ (st[a^]t`[i^]s*t[i^]sh"an), n.
   [Cf. F. statisticien.]
   One versed in statistics; one who collects and classifies
   facts for statistics.
   [1913 Webster]

WordNet (r) 3.0 (2006):

statistician
    n 1: a mathematician who specializes in statistics [syn:
         statistician, mathematical statistician]
    2: someone versed in the collection and interpretation of
       numerical data (especially someone who uses statistics to
       calculate insurance premiums) [syn: statistician,
       actuary]