Apps / SPC
Build control limits for X-bar/R, p, np, c, and u charts from operator-entered subgroup data. The app calculates UCL, LCL, and center line values, flags out-of-control signals, checks Western Electric rules, and renders live chart previews.
Generator
Control limit basis: X-bar/R, p, np, c, u
The operator data grid below adapts to the chart type. For X-bar / R, enter subgroup measurements. For p, np, c, and u charts, enter defect or defect-count data by subgroup.
Each row is one subgroup. Update the grid and click Generate limits.
Primary Chart
Secondary Chart
Instructions
Select the chart type that matches the data you collect on the shop floor. For X-bar / R, use rational subgroups of measured values. For p and np charts, enter defectives by subgroup. For c and u charts, enter defect counts, with u charts also using opportunities or units.
The app checks classic Western Electric patterns on the primary chart. Rule 1 flags any point beyond 3 sigma. Additional alerts watch for 2 of 3 beyond 2 sigma, 4 of 5 beyond 1 sigma, and runs of 8 on one side of the center line.
Use the live chart preview for operator review, escalation discussions, and quick SPC coaching. If the chart is unstable, address special causes before using the data for capability studies or process-release decisions.