1. a number that represents a measurement of some characteristic, construct, variable, or other item of interest.

2. any function of the observations in a sample that may be used to estimate the unknown but corresponding value in the population. Examples include measures of central tendency (e.g., the mean, median, mode), measures of dispersion (e.g., standard deviation, variance), and distributional attributes (e.g., skewness, kurtosis). Statistics often are assigned Roman letters (e.g., M, s), whereas the equivalent values in the population (called parameters) are assigned Greek letters (e.g., μ, σ). —statistical adj.