Two-dimensional histograms (the term was first used by Pearson, 1895) present a graphical representation of the frequency distribution of the selected variable(s) in which the columns are drawn over the class intervals and the heights of the columns are proportional to the class frequencies.

STATISTICA offers several types of 2D histograms: Regular for single variables, Double-Y for plotting two variables\histograms on the same graph each with a separate frequency scale, Multiple for plotting multiple variables\histograms on the same graph with a common frequency scale, and Hanging Bars for hanging the frequency columns of a variable from the normal curve. The latter type provides a "visual test of normality" to identify areas of a variable's distribution that show discrepancies between observed and predicted normal frequencies.

Any of the distributions specified in Fitted Functions for Histograms can be displayed on Regular, Double-Y, or Multiple histogram graphs for visual comparison. Histogram intervals or categorization can be defined by any of the options discussed in Methods of Categorization.

See also, Graphs - 2D Histograms and the Conceptual Overview for 2D Histograms.