Histograms are of five types. They are:

• Bell shaped: It can be applied for concepts such as average and standard deviation.
• Double peaked: It is used to compare two different processes with different centres.
• Plateau distribution: It is used when the process is not well-defined.

Since the process is handled by different people in different ways, different measurements arise with none standing out. Plateau distribution is used to define an efficient process.

• Comb type distribution: It is a result of the faulty construction of the histogram, with data combined together into a group called „greater than?.

• Skewed distribution: The skewed distribution is asymmetrical since a natural limit prevents outcomes on one side. A distribution of analyses of a very pure product would be skewed, as any product cannot be more than 100 percent pure.

The figure shows the type of histogram.

Figure: Types of Histograms