A histogram is a lot more than a bar chart! In a histogram, the area of the bar, NOT its height, is proportional to frequency. Bars do not have to be of equal width. The height of each bar is called the frequency density.

## Software/Applets used on this page

## Glossary

### density

the ratio of the mass of an object to its volume

### frequency

Of a function: the rate of repetition of a periodic function.

In statistics: the number of occurances of a value

In statistics: the number of occurances of a value

### frequency density

The frequency density of a frequency distribution is given by

(class frequency)/(class width).

(class frequency)/(class width).

### histogram

A statistical diagram for continuous data similar to a bar chart but where the area of each bar is proportional to the frequency.

### union

The union of two sets A and B is the set containing all the elements of A and B.