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A histogram is constructed from a frequency table. The intervals are shown on the X-axis and the number of scores in each interval is represented by the height of a rectangle located above the interval. A histogram of the response times from the dataset Target RT is shown below.

Histogram

The shapes of histograms will vary depending on the choice of the size of the intervals. Click here to see an interactive histogram demonstrating the effect of changing the size of the intervals.

A bar graph is much like a histogram, differing in that the columns are separated from each other by a small distance. Bar graphs are commonly used for qualitative variables.

Next section: Stem and Leaf Displays