Subgroup Data (Means & Ranges)
| Subgroup | Mean (x̄) | Range (R) |
|---|
items
Process Stability Index
Points out of control (%)--%
StableCautionUnstable
Awaiting input
Control Limits
X̄̄ (Center line)
--
UCL (X-bar)
--
LCL (X-bar)
--
Out‑of‑control flags
0
SPC Formulas
X̄̄ = (Σx̄i)/k R̄ = (ΣRi)/k
UCLx̄ = X̄̄ + A2·R̄ LCLx̄ = X̄̄ − A2·R̄
UCLR = D4·R̄ LCLR = D3·R̄
Constants A2, D3, D4 from ASTM E2587 based on subgroup size n.
Out‑of‑control: beyond ±3σ limits, or 7+ consecutive points on same side of center.
X̄ Control Chart (with zone lines)
Range Chart (R chart preview)