The Silent Shift

You're a senior quality engineer at an automotive stamping plant. The plant runs two 12-hour shifts on the same press, making the same part. Management has been charting the data combined -- both shifts on one X-bar chart. The chart looks erratic: high variation, possible out-of-control signals. The plant manager wants to know: is the process capable, or do we need a new press? You have 20 subgroups of combined data and the production logs.