#statistic  a datum that can be represented numerically
  supertype:  #datum__data_point  an item of factual information derived from measurement or research
  subtype:  #average__norm  a statistic describing the location of a distribution: "it set the norm for American homes"
     subtype:  #age_norm__agenorm  the average age at which particular performances are expected to appear
     subtype:  #modal_value__mode  the most frequent value of a random variable
     subtype:  #median_value__median  the value below which 50% of the cases fall
     subtype:  #mean_value__mean  an average of n numbers computed by adding some function of the numbers and dividing by some function of n
        subtype:  #arithmetic_mean__first_moment__firstmoment__expectation__expected_value  the sum of the values of a random variable divided by the number of values
        subtype:  #geometric_mean__geometricmean  the mean of n numbers expressed as the n-th root of their product
        subtype:  #harmonic_mean  the mean of n numbers expressed as the reciprocal of the arithmetic mean of the reciprocals of the numbers
  subtype:  #demographic  a statistic characterizing human populations (or segments of human populations broken down by age or sex or income etc.)
  subtype:  #deviation  the difference between an observed value and the expected value of a variable or function
     subtype:  #outlier  an extreme deviation from the mean
     subtype:  #mean_deviation_from_the_mean__mean_deviation  the arithmetic mean of the absolute values of deviations from the mean of a distribution
  subtype:  #moment.statistic  the n-th moment of a distribution is the expected value of the n-th power of the deviations from a fixed value
     subtype:  #second_moment  the expected value of the square of the deviations of a random variable from the point of origin
     subtype:  #variance  the second moment around the mean; the expected value of the square of the deviations of a random variable from its mean value
        subtype:  #standard_deviation  the square root of the variance
        subtype:  #covariance  statistical measure of the variance of two random variables measured in the same mean time period
  subtype:  #nonparametric_statistic__nonparametricstatistic__distribution_free_statistic  a statistic computed without knowledge of the parameters of the distribution from which observations are drawn
     subtype:  #rank-order_correlation_coefficient__rank-order_correlation__rank-difference_correlation_coefficient__rank-difference_correlation  the most commonly used method of computing a correlation coefficient between the ranks of scores on two variables
     subtype:  #Kendall_test  any of several nonparametric measures of correlation (used when the assumptions of standard correlational analysis are not met)
        subtype:  #Kendall_partial_rank_correlation  a nonparametric measure of partial correlation
        subtype:  #coefficient_of_concordance  a coefficient of agreement (concordance) between different sets of rank orderings of the same set of things
        subtype:  #tau_coefficient_of_correlation__Kendall's_tau__Kendall_rank_correlation  a nonparametric measure of the agreement between two rankings
     subtype:  #phi_coefficient__phicoefficient__phi_correlation__phicorrelation__fourfold_point_correlation  an index of the relation between any two sets of scores that can both be represented on ordered binary dimensions (e.g., male-female)
  subtype:  #parametric_statistic  any statistic computed by procedures that assume the data were drawn from a particular distribution
     subtype:  #regression_coefficient  when the regression line is linear (y = ax + b) the regression coefficient is the constant (a) that represents the rate of change of one variable (y) as a function of changes in the other (x); it is the slope of the regression line
     subtype:  #correlation_coefficient__correlationcoefficient__coefficient_of_correlation__correlation  a statistic representing how closely two variables co-vary; it can vary from -1 (perfect negative correlation) through 0 (no correlation) to +1 (perfect positive correlation); "what is the correlation between those two variables?"
        subtype:  #Pearson_product-moment_correlation_coefficient__product-moment_correlation_coefficient  the most commonly used method of computing a correlation coefficient between variables that are linearly related
        subtype:  #multiple_correlation_coefficient  an estimate of the combined influence of two or more variables on the observed (dependent) variable
        subtype:  #biserial_correlation_coefficient__biserial_correlation  a correlation coefficient in which one variable is many-valued and the other is dichotomous
        subtype:  #split-half_correlation__chance-half_correlation  a correlation coefficient calculated between scores on two halves of a test; taken as an indication of the reliability of the test
        subtype:  #tetrachoric_correlation_coefficient__tetrachoriccorrelationcoefficient__tetrachoric_correlation__tetrachoriccorrelation  a correlation coefficient computed for two normally distributed variables that are both expressed as a dichotomy
  subtype:  #time_series  a series of values of a variable at successive times
  subtype:  #vital_statistics  data relating to births and deaths and health and diseases and marriages
  subtype:  #correlational_statistics__correlation  a statistical relation between two or more variables such that systematic changes in the value of one variable are accompanied by systematic changes in the other
     subtype:  #curvilinear_correlation__curvilinearcorrelation__nonlinear_correlation__skew_correlation  any correlation in which the rates of change of the variables is not constant
     subtype:  #partial_correlation__partialcorrelation  a correlation between two variables when the effects of one or more related variables are removed
        subtype:  #first-order_correlation__firstordercorrelation  a partial correlation in which the effects of only one variable are removed (held constant)
     subtype:  #positive_correlation__direct_correlation  a correlation in which large values of one variable are associated with large values of the other and small with small; the correlation coefficient is between 0 and +1
     subtype:  #negative_correlation__indirect_correlation  a correlation in which large values of one variable are associated with small values of the other; the correlation coefficient is between 0 and -1
     subtype:  #spurious_correlation  a correlation between two variables (e.g., between the number of electric motors in the home and grades at school) that does not result from any direct relation between them (buying electric motors will not raise grades) but from their relation to other variables

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