Posted on September 24, 2009 by


The histogram is graphical representation of data. It is a tool of the PMBOK®’s Perform Quality Control process, but can be used in any field where this type of data is to be displayed. The example here is from Carl’s Car Restoration business. For marketing purposes, he wanted to see what ages his customers were. His customers ranged from age 39 to 55. There were no customers ages 40, 53, or 54. The mode (most common) age was 46, with 5 customers being that age. Note that the bars are touching each other because of the continuous nature of the age variable. For example, someone 42 years old could be almost 43, and actually be closer in age to those who just turned 43 than they are to the 42-year-olds in their own category. By having the bars touch in a histogram, this continuous nature is displayed. If the x-axis were composed of a set of categories, there would be spaces between the bars and it would be called a Bar Chart.

Histogram Age Customers