Pareto analysis identifies the most important quality-related problems to resolve in a process.
The Pareto principle (also known as the 80/20 rule) states that for many events, roughly 80% of the problems come from 20% of the causes. This statement is merely a rule of thumb and is not an immutable law of nature. More generally, a small subset of issues tend to cause most problems, and it is useful to identify those issues as they have the most impact on the process.