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Histogram
A chart that displays the frequency distribution of continuous numeric data using adjacent bars over contiguous intervals (bins).
In Plain English
A histogram shows how continuous data is distributed by chopping the number line into intervals, or bins, and drawing a bar over each one, with height proportional to how many observations fall in that interval. Unlike a bar chart, the bars touch, since the underlying intervals are contiguous, not separate categories.
Definition
A histogram displays the frequency distribution of continuous numeric data by dividing the range of values into contiguous intervals, or bins, and drawing a bar over each bin with height proportional to the frequency (or relative frequency) of observations falling within it. Bars in a histogram are conventionally drawn adjacent, with no gaps, reflecting the continuous nature of the underlying variable.
Properties
- Bin width is the single most consequential choice in constructing a histogram -- too wide, and real structure like bimodality gets smoothed away; too narrow, and random sampling noise can look like meaningful pattern.
- A histogram is a direct visual estimate of a variable's underlying probability density -- as the sample size grows and bin width shrinks appropriately, a histogram increasingly approximates the shape of the true density function.
- Several data-driven rules exist for choosing bin width or bin count automatically, such as the Freedman-Diaconis rule and Sturges' rule, though visual judgment and domain knowledge often still improve on a purely automatic choice.
At a Glance
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