Drop your data, then pick the chart that matches it: I‑MR for one reading at a time, X̄‑R or X̄‑S for subgroups (each row a subgroup, or a single column reshaped by subgroup size), and p or np for go/no‑go defect counts. The tool sets the center line and 3σ control limits, then flags any point beyond the limits or any run that breaks the basic rules. Stabilize first — a process must be in control before its Cp / Cpk means anything. Feed a signal into a 5 Whys or Fishbone to chase the special cause.