Histogram vs Pareto Chart is the 29th post in our PMP Concepts Learning Series.
Designed to help those that are preparing to take the PMP or CAPM Certification Exam, each post within this series presents a comparison of common concepts that appear on the PMP and CAPM exams.
Histogram vs Pareto Chart
There are number of charts used to evaluate and analyze quality results within a project. Two charts that are similar and often confused are the histogram and Pareto chart.
Histogram
A histogram is a type of bar chart showing a distribution of variables. A histogram represents each attribute or characteristic as a column and the frequency of each attribute or characteristic occurring as the height of the column.
Pareto Chart
A Pareto chart is a specific type of histogram that ranks causes or issues by their overall influence. A Pareto chart assists in prioritizing corrective actions as the issues with the greatest impact are displayed in order. In addition, the Pareto chart includes an arc representing the cumulative percentage of the causes.
A Pareto chart is named after Pareto’s Law that states that a relatively small number of causes will typically produce a large majority of the problems or defects. This is commonly known as the 80/20 rule, where 80% of the problems are due to 20% of the causes.
Example
A histogram may be used to represent the number of students who scored between a certain score range, such as 0 to 20%, 20 to 40%, etc.
A Pareto chart may be used to analyze the causes of customer dissatisfaction. The causes would be ordered by frequency of occurring, allowing the team to focus on those issues with the biggest impact on customer satisfaction.
Summary
A histogram is a bar graph that illustrates the frequency of an event occurring using the height of the bar as an indicator.
A Pareto chart is a special type of histogram that represents the Pareto philosophy (the 80/20 rule) through displaying the events by order of impact.
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