Cycle Time Shift × Line (heatmap)

45 cycle-time measurements (in seconds) across three shifts (early/late/night) and three production lines (L1/L2/L3) — 5 readings per combination. The heatmap reveals two effects at once: a line effect (L3 ≈ 30 s slower than L1) and a shift effect (night ≈ 10 s slower than early). The (night, L3) cell at 82 s is the clear worst case — a perfect starting point for the Analyze phase.