Frequency tables
A computer is normally used to draw histograms, but it is instructive to consider how one might be drawn by hand. The class heights in a histogram are found from the class frequencies, so we consider in more detail how to find a table of frequencies .
Ages of patients
Technical support time
Drawing histograms with mixed class widths (advanced)
When all classes do not have the same width, the rectangle height for any class should be its density,
Since the area of a rectangle is given by its height (the density) times the class width, this definition ensures that area equals relative frequency.
Lengths of wood chips