I have produced 50 units and after testing, I notice that 3 of them have a failure. So I change my production process and produce another 50 units. This time, I detect no failures. Did I resolve the issue? Can I quantify how sure I can be that the problem is solved?
How should I approach this problem from a statistical point of view?
Finally, what if the situation was reversed, i.e. I had zero failures when measuring 50 units but after a change in the process, I find 3 failures in 50 units. Is this same situation as before? Could I conclude that the process is significantly different?