Recently I sat down and asked our bug database about my last four years of being a software tester. Here are some statistics I found in it:
This makes 91 bugs per year, or 1.75 per week. 68.96% of the bugs I opened got fixed, 9.07& are invalid, 7.42% are duplicated, 4.4% will not be fixed, 3.85% could not be reproduced, while nearly 5% of the bugs I opened are still either new, someone works at them or they needed to be reopened.
What does this tell you about me as a tester? Am I a good tester? A bad one? A mediocre? Were my bug reports always clear? Did they motivate the responsible developer to fix them? How did the bad reports distribute over the years?
Now, these are the more interesting questions to ask in order to make any sense on whether I am a good tester or not. Mere bug counts or percentage values do not reveal anything about this. So, rather than managing by the numbers, maybe manage by working with the individuals. The famous paper on software engineering metrics from Kaner and Bond has more on this.