Observed defects and a control-chart claim

A fictional project records one hundred and twenty defects in an agreed test window. Seventy concern interfaces, twenty-five concern migration, fifteen concern the user interface and ten concern performance. The categories are mutually exclusive under the supplied recording rule. A team member says the first two categories prove an eighty-twenty law and reveal the exact root cause without further work. Another plots daily error counts but labels the customer’s maximum acceptable count as a statistical control limit. The project needs a prioritized investigation and defensible acceptance evidence. All figures are exercise data, not an observed national industry rate or an official examination blueprint. The task is to distinguish counting, prioritization, statistical process behavior and conformance with specified requirements.