EWMA (Exponentially Weighted Moving Average) weights recent data more heavily and is more sensitive than the Xbar chart to small, persistent drifts. Control limits start wide and stabilize over time.

CUSUM (Cumulative Sum) accumulates each point's deviation from target; it is most sensitive to persistent small drifts of the mean. The tabular method uses h (decision interval) to signal.

Median-R (Median-Range) uses subgroup medians instead of means, making it more robust to outliers; the range chart is unchanged. Suitable for manual field recording and slightly skewed data.

Laney P′/U′: when sample sizes are large and p/u charts repeatedly go out of control due to overdispersion (excessive data variation), the Z moving range corrects σ to produce P′/U′ adjusted control limits.

Z-MR: first standardize individual values as Z=(x−μ)/σ, then plot the Z chart (limits ±3) and the Z moving-range chart. Products of different units/engineering are unified to one scale and share one set of out-of-control rules.

G/T Rare Events: when defects/incidents are very rare, monitor the interval (time or number of parts) between consecutive events. The t-chart transforms interval t to y=t^0.2777 before plotting; a significantly shorter interval means events are becoming more frequent (worsening).

Zone Chart: divides the control chart into C/B/A zones at ±1σ/±2σ/±3σ and applies zone rules: one point beyond ±3σ; 2 of 3 consecutive points beyond ±2σ on the same side; 4 of 5 consecutive points beyond ±1σ on the same side; 9 consecutive points on one side.

Precontrol: set target / target ± spec, then draw two precontrol lines P_L, P_U at the midpoint between center and spec limits. A red zone (out of spec) or 2 consecutive points in the same-side yellow zone means stop and adjust; green zone means normal. Suited to quick patrol checks in mass production; no need to compute control limits first.