You need to Defect Density Like Categorize the bugs to different categories Unit, Functional etc., Then map them to your Test Cases.
By doing all this you will be able to get the following answers.
1. How good were your test cases?
2. Which part of the application you need to concentrage to get more no. of bugs
3. If you get more Unit level bugs, then yu need to concentrate more on Unite testing. So that you can devote a testing towards finding more functional bugs.
4. What is the % of bugs you found against Test Cases.
5. If similiar kind of applications we are going to test then which are the part to be concentrated for throughness et.,