The Collaborative International Dictionary of English v.0.48:

Statistics \Sta*tis"tics\ (st[.a]*t[i^]s"t[i^]ks), n. [Cf. F.
   statistique, G. statistik. See State, n.]
   1. The science which has to do with the collection,
      classification, and analysis of facts of a numerical
      nature regarding any topic. Specifically: The science
      dealing with collection, tabulation, and analysis of facts
      respecting the condition of the people in a state.

   Note: [In this sense grammatically singular.]
         [1913 Webster]

   2. pl. Classified facts of a numerical nature regarding any
      topic. Specifically:
      (a) Numerical facts respecting the condition of the people
          in a state, their health, their longevity, domestic
          economy, arts, property, and political strength, their
          resources, the state of the country, etc., or
          respecting any particular class or interest;
          especially, those facts which can be stated in
          numbers, or in tables of numbers, or in any tabular
          and classified arrangement.
      (b) (Sport) Numerical facts regarding the performance of
          athletes or athletic teams, such as winning
          percentages, numbers of games won or lost in a season,
          batting averages (for baseball players), total yards
          gained (for football players). The creation and
          classification of such numbers is limited only by the
          imagination of those wishing to describe athletic
          performance numerically.

   Syn: stats.
        [1913 Webster +PJC]

   3. The branch of mathematics which studies methods for the
      calculation of probabilities.
      [PJC]

WordNet (r) 3.0 (2006):

statistics
    n 1: a branch of applied mathematics concerned with the
         collection and interpretation of quantitative data and the
         use of probability theory to estimate population parameters

The Free On-line Dictionary of Computing (30 December 2018):

statistics

    The practice, study or result of the
   application of mathematical functions to collections of
   data in order to summarise or extrapolate that data.

   The subject of statistics can be divided into descriptive
   statistics - describing data, and analytical statistics -
   drawing conclusions from data.

   (1997-07-16)