I would say Testing Efficiency would be the number of manual test run per hour and Defect Removal Efficiency is the amount of time it took from writing the defect report until the defect fix was delivered.
Sort of goes to show that many of the terminologies can have multiple meanings.
Testing is a practice, not a science. I've got to go practice some more.
Success is the ability to go from one failure to another with no loss of enthusiasm.
~ Winston Churchill ~
In QC there is a tendency to identify what is done as the finding of bugs when we are really ensuring that the product being tested is ready for use by the target audience. Finding bugs and getting them resolved is a big step in this but not the end result of what we do.
I have not failed. I've just found 10,000 ways that won't work" --Thomas Edison
Efficiency is a productivity metrics meaning how fast one can do something. Hence Testing efficiency metric can be "No. of test cases executed per hour or per person day". This explains how efficient (i.e. fast) the person is at testing.
DRE is a measure to detect defects before delivery.It is calculated as a percentage of the defects identified and corrected internally with respect to the total defects in the complete project life cycle. Thus, DRE is the percentage of bugs elimiated by reviews, inspections, tests etc.
I suppose it's obvious that English is NOT my native language... but I've noticed too many times the term "efficiency" used instead "effectiveness".
Efficiency usually measures the results of an activity per costs for that activity. For testing, it's a litle more difficult because the results should be mainly the possible loses due to a certain discovered defect (which is very difficult to estimate, and almost impossible to be really CALCULATED), not the defect itself.
Measuring the total amount of possible loses for all discovered bugs, versus the costs of testing we'll have a measure of efficiency.
Considering the original post, the "Overall defect removel efficiency" should be "Overall defect removel effectiveness" which is a measure of number of discovered defects during project life versus total number of defects (including the defects discovered in production)
Well... Going by the definition of efficiency, it should be the ratio of output and input. Hence for me, it would be number of defects detected, divided by number of total defects. Thus testing efficiency for a phase (say design) would be number of defects detected in the design phase divided by the sum of undetected defects from RA phase and defects injected in design phase.
I have seen organizations calculating testing efficiency by dividing the number of defects detected by the time spent on testing and I wonder how can that be a measure of efficiency!!
If I am an excellent tester and I am able to find only one defect (because there is only one defect) after testing a heavy code for 10 hours, does that mean my efficiency is that fraction??