The Histogram

Histogram is a bar graph.

The histogram is the most common graphical display for showing the statistical distribution of a collection of numbers. It is similar to a bar chart except that it is a graphical representation of a frequency distribution. The frequency of the bar is represented by its area rather than its height. For example, given a list of the areas of all farms in a country, a good indication of the relative numbers of farms of various sizes could be obtained by:

• rounding farm sizes to the nearest 10 hectares;
• counting the numbers of farms with areas (0-10 hectares), (10- 20 hectares), (20-30 hectares), and so on.
• Drawing rectangles with these intervals as bases and with heights proportional to the counts.

Such a graph called a histogram. Because the rectangles are usually bar shaped – that is, much taller than wide – a histogram is also known as a bar graph. The number of intervals is chosen for convenience. If the graph includes too many intervals, the data are not sufficiently summarized. Too few intervals, however, means that too much information is lost.