I have some idea about defect leakage. Can anyone let me know what is the correct definition or term of the defect leakage formula?
Defect leakage formula is defined as -
Number of Defects slipped / (Number of Defects raised - Number of Defects withdrawn)
Example: In production the customer raises 21 issues, during your tests 267 Issues were reported but there were 17 invalid defects (e.g. because of wrong tests, mistake by tester, error in test environment...)
Then your Defect Leakage Ratio would be:
[21/(267-17)] x 100 = 8.4%
Defect leakage is the metric that use to identify the efficiency of QA. As mentioned by demouser123, it's calculated against the number of slipped issue - the number of issue that found by customer by using delivered/released application