I have read several articles by Capers Jones, who states that:
Defect Detection Efficiency (DDE): percentage of defects found after release
Defect Removal Efficiency (DRE): percentage of fixed defects when compared to customer reported issues.
In the further text, he gives an example of DRE: when the development team found and fixed 90 defects, and the customer then finds 10, DRE=90%.
There is a note about the difference between DDE and DRE, stating that some companies choose not to fix all found defects before release, making DRE thus lower.
But how are those unfixed issues reflected? Let's say I found 100 defects and fix only 50. The customer, for some reason, found only 5. Following the stated process, DRE then should be 50/50+5=90%, even when I left 50 defects unfixed.
Is that truly correct? To me it seems counterintuitive that when I leave 50% of defects unfixed, in a situation when the customer found nothing, DRE would be 100%.