Probably I am missing some key aspect here, because I simply have no idea how this metric is supposed to tell me anything described by the authors:
Defect Open and Close rate = (Defects found during testing in a release / (Defects found during testing in a release + Defects found after release) *100
What is it?
While there are numerous defect statuses which indicate the current state of an identified flaw, they can typically be categorized as either open or closed.
Why is it important?
The sheer number of defects that are encountered during a project’s run can make them difficult to keep tabs on. If team members are not diligent about measuring the current status of their program’s flaws, certain defects could slip through the cracks and show up in the finalized release. Furthermore, comparing the frequency of open defects with close rates will also provide insight into the ability of testers and developers to work together to identify and address software issues.