I have a question regarding the percentage of defect requirements of the total set of requirements for a certain System. Is there any literature, that has some figures (i.e. mean) how many requirements of the whole set are defect (are not feasible, traceable, verifiable, complete etc.)?

I couldn't find anything on IEEE, ACM and google scholar.

If someone knew a source of such a study, i would be glad to hear from you!

  • Are you asking how many defects are found in requirements? Or are you asking how many requirements are actually defects? Either way, I don't think anyone is able to answer this - can you clarify your question?
    – dvniel
    Commented Jun 26, 2018 at 14:17

1 Answer 1


Assuming that you are asking if there is some kind of typical measure of how many requirements for a given system are in fact incorrect in some way, the simple answer is it depends.

Is a requirement that turns out to be unusable once implemented a defective requirement?

What about one that the customer insists they want then never use?

Do you include the additional requirements that can't be known until well into development?

This is why software development has changed from trying (and failing) to enforce strict process models to a more flexible agile-like approach. Unlike manufacturing, every software project is different, and every software project can be completed in a number of different ways and still satisfy the customer - in short, software development is a wicked problem and apart from small, clearly bound projects is likely to stay that way for the foreseeable future.

So, you're unlikely to find any references on how many requirements are typically defective in some way. You'd do better looking for resources about keeping the requirements up to date as a project evolves.

  • Thanks for your answer! Yeah I thought it would go in this direction. It depends strongly on the term "defect". I am currently working on a small project and did an analysis of the requirements and if they posses the properties of "good" requirements specified by the ISO 29148 standard. Found some issues with them and wanted to compare the figures of that to some industry findings. But your answer is correct and I'll accept it of course, thanks! Commented Jun 26, 2018 at 18:58

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