When dealing with attribute data, you can use a control chart to make this comparison. Determine what set of conditions contribute to the acceptable and unacceptable areas using the 6Ms, i.e., Man, Machine, Method, Material, Measurement, or Mother Nature.
There are many samples when the defective rates are very low and also when they are very high. Is that difference because of different operators, different machines, different lots of material, different methods being used, etc. It is your job to determine the largest sources of variation in the process and put controls in place to eliminate or reduce them!