Pareto Principle in Software Testing

by Nataliia Vasylyna | February 25, 2011 11:10 am

Note: The article was updated in February 2021.

The Pareto Principle states that 20% of efforts bring 80% of results, and the other 80% of efforts bring only 20% of results.

The first person to discover this pattern was Vilfredo Pareto, an economist from Italy. He concluded that 80% of all property in Italy belonged to only 20% of the population. He also suggested that this pattern could be found in many other areas.

Eventually, the principle received the name “Pareto Principle” and was applied to a number of different fields and industries. Quality Assurance (QA[1]) is one of them.

Pareto principle in software testing

In software testing, the Pareto Principle is commonly interpreted as “80% of all bugs can be found in 20% of program modules”. Moreover, a half of the modules may contain no bugs at all. The numbers, of course, are approximate, and the real ratio can be 30% and 70%, etc. The idea is that the distribution of software glitches[2] is not equal, and they usually cluster in a certain part of the code. It is especially typical of the most severe defects.

Applying the Pareto Principle to QA activities[3] helps to decrease testing time and to increase its efficiency. But you should know how and when to use it in order to achieve better results.

QA and testing banner[4]

Here are several ways to apply the Pareto Principle in software testing:

The Pareto Principle requires good analytical and logical skills. But it can be a very powerful tool for decreasing the amount of bugs while reducing the overall testing effort.

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Endnotes:
  1. QA: https://qatestlab.com/resources/knowledge-center/quality-assurance-control/?_ga=2.217318290.5865719.1612456643-593094287.1607934112
  2. software glitches: https://blog.qatestlab.com/2015/03/03/what-is-the-essence-of-software-bugs/
  3. QA activities: https://blog.qatestlab.com/2011/12/21/quality-assurance-activities-in-software-processes/
  4. [Image]: https://qatestlab.com/services/?utm_source=Blog&utm_medium=Post&utm_campaign=services
  5. Definitions and Meaning: Error, Fault, Failure and Defect: https://blog.qatestlab.com/2011/12/06/definitions-and-meaning-error-fault-failure-and-defect/
  6. White Box Test Techniques. Data Flow Testing: https://blog.qatestlab.com/2011/09/23/white-box-test-techniques-data-flow-testing/
  7. Black Box Test Techniques. Random Testing: https://blog.qatestlab.com/2011/09/19/black-box-test-techniques-random-testing/

Source URL: https://blog.qatestlab.com/2011/02/25/pareto-principle-in-software-testing/