Statistics is the study of the collection, organization, analysis, interpretation and presentation of data. In this section we provide descriptive statistics, that is, functions of the input which each summarize an intuitive aspect of the given input. The most important descriptive statistics are those describing central tendency, such as mean, median, and mode, and those describing dispersion, such as variance, standard deviation, and range. Other statistics include those describing dependency between two or more data-sets, such as correlation, and mutual information. Under probabilistic assumptions, i.e. an underlying population distribution, the descriptive statistics can often be shown to be estimators, with varying properties, of the parameters of the population distribution.