What is a Histogram?
In very simple terms, we can say that “Histogram is a graph that displays numerical data in a picture form, showing group data on one axis and percentage of data that falls into each group on the other axis.”
It is important to understand that, in the histogram, the groups are continuous groups.
Histogram chart Example
In the below example, there are a total of 60 students, and they are grouped in 5 kg range weight groups. The range of each group is 5kg, and importantly the succeeding group immediately starts after its proceeding group. Thus these groups are continuous groups. Now, representing them in graphical form gives us a histogram.
| Weight (in kg) | Number of students |
| 30-35 | 7 |
| 35-40 | 12 |
| 40-45 | 25 |
| 45-50 | 9 |
| 50-55 | 5 |
| 55-60 | 2 |
| Total Students | 60 |
Histograms display data in the form of bars or columns.
It is important to understand that a histogram displays data without reference to time.
In quality management, histograms are widely used in various activities such as showing the number of defects per deliverable, the number of times a process failed compliance, etc.
Check the Seven Basic Quality Tools.