Pareto
What happens often is not always what costs most. Explore a sample, switch the ranking, then try your own numbers.
Take the investigation further
Leave with a project charter, a defensible baseline, an evidence log, a trial decision and a response plan.
Check the method with a worked example
Use one comparable measure—counts, minutes or cost—and non-overlapping categories. A descending chart helps choose an investigation; it does not prove the cause.