Exam CQE topic 1 question 67 discussion

As a commonly used problem solving technique, which of the following would be the BEST application of a Pareto chart?
I. To determine when to make proactive adjustments to a process.
II. To differentiate between major and minor problem areas.
III. To gather data and to design experimental controlled changes.
IV. To evaluate the results of other problem solving techniques upon the product or service.