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Defect Density


By detecting defects and errors during the early stages of software development one can ensure the quality, performance, scalability, features, security, as well as other important elements of the software. Moreover, by conducting defect detection software developers can validate whether the application is being built as per the demands of the client and make all the necessary changes if required. To ensure that the product’s effectiveness is apt and correct, software engineers use defect density, which is a metric that states, “The more defects in the software, the lower the quality is”. Though this metric may seem insignificant to the majority of people, it is a key quality indicator. Therefore, elaborated for your reference, here is a discussion on defect density.

What Is Defect Density?

Defect Density is the number of confirmed defects detected in the software or a component during a defined period of development or operation, divided by the size of the software. It is one such process that enables one to decide if a piece of software is ready to be released. Moreover, the importance of defect density is immense in Software Development Life Cycle (SDLC), as it is used to compare the relative number of defects in various software components, which further helps in identifying candidates for additional inspection or testing as well as for re-engineering or replacement. Also, identifying defect prone components is made easy through defect density, which allows the testers to focus the limited resources into areas with the highest potential return on the investment. This further helps organisations and their businesses reach great heights of success, as they are able to deliver software and applications that are secure, safe, bug free and more.

Defect Density Formula:

The defect density could be defined as the value of the total defects, which are known to the size of the software product calculated:

Defect Density = Total defect/Size.

There is no fixed standard for defect density, however, studies suggest that one Defect per 1000 lines of codes (LOC), which is generally considered as a sign of good project quality. This standard of defect density is also known as KLOC. Defect density, therefore, is a measure showing the ratio of defects against the size of a development (number of defects/size), in which the size is typically expressed in terms of Function Points (FP), Impact points or other ‘points’ measures. Hence, following are the steps for calculating defect density:

  • Collect the raw material, i.e., testers will require the total number of defects detected while developing the software product.
  • Calculate the average number of defects/ Functional area or line of code (LOC).
  • For example: For a particular test cycle there are 30 defects in 5 modules or components. Therefore, the density will be:
    Total no. of defects/ KLOC.
    30/15 = 0.5

Hence, the density is 1 defect for every 2 KLOC.

Uses of Defect Density:

Defect density is a recognised industry standard and it uses are numerous. It is a process of calculating the number of defects per development, which helps software engineers in determining the areas that are weak as well as that require rigorous testing. Defect density is also used to compare subsequent releases of a product, to track the impact of defect reduction and quality improvement activities. Moreover, through this technique, one can compare differences between products or product lines. Other uses of defect density are:

  • Predict the remaining defects when compared to the expected defect density.
  • Determine if the amount of testing is sufficient.
  • Establish a database of standard defect densities.
  • Conveys the progress, productivity and quality of the product.
  • It provides information regarding the product, which helps in deciding whether it is fit for use or not.
  • As a module with high defect density requires mending and work, defect density helps in identifying them and promotes call for action.

Factors Affecting Defect Density Metrics:

Before moving towards the advantages of defect density, it is important for us to know the elements that can affect the result as well as the outcome of defect density. As defect density is the measure of the total known defects divided by the size of the software entity being measured, it is necessary to ensure that all the conditions are met before it is initiated. This not only enables developers to get accurate results, but also allows them to track all the affected areas properly. These factors are:

  • The complexity of the code.
  • The type of defects taken into account for the calculation.
  • Time duration which is considered for defect density calculation.
  • The skills of the developer and tester.
  • Another factor that affects the metrics of defect density is the usability of the software under development.

Advantages of Defect Density:

The advantages of defect density are several as it caters to numerous requirements of a software tester and ensures that all the defects are measured accurately. With the assistance of defect density, a software engineer can be confident about the quality and performance of the software, as it allows them to measure the effectiveness of software testing. The other advantages of defect density are mentioned below:

  • Can track and detect high risk components.
  • Useful in identifying the areas for correction or improvement.
  • It helps in identifying the training needs for various resources.
  • Developers and testers can estimate the testing and rework required due to bugs and errors in the software.
  • With the assistance of defect density, one can differentiate defects in components/software modules.
  • Before the release of the product, one can determine whether the testing is sufficient.
  • Can ensure database with a standard defect density.

Conclusion

The above discussion reflects the importance as well as the benefit of using defect density during the process of software development. Though defect density is considered insignificant and unnecessary by several software engineer, it is one of the best way to judge the areas that are highly affected by bugs and errors. A recognised industry standard, Defect Density is a metric that states that “The more defects in the software, the lower the quality is”. Therefore, it calculates the defects that are in the software product divided by the total size of the software or a component being measured. With the assistance of this metric, software engineers, developer, testers and more can measure the testing effectiveness and differentiate defects in components or software modules. Moreover, they can also estimate the testing and rework required due to the detected defects and bugs. Hence, by performing defect density, one can not only calculate the defects per developed software, but they can also ensure its effectiveness, quality, performance, and more.