A histogram is a chart that presents numerical data. In a histogram, the height of each bar or column represents the absolute frequency of each category in the distribution.

In a previous post we presented the frequency distribution for the companies in the Dow Jones Industrial Average by market capitalization. The same data can be presented in a histogram as follows.

A histogram can effectively present a large amount of numerical data for quick inspection. Observing the shape, center, and spread of a distribution can be helpful for understanding it. Depending on the type of data being analyzed, a histogram can be presented using either absolute or relative frequencies.

A frequency polygon could show the same data as a line chart connecting the midpoints of each category. Alternatively, a cumulative frequency distribution chart would show the number of observations below each value.