Quality Control Edition

Control charts with detection rules, phases, and stratification Shewhart variable and attribute charts, CUSUM, EWMA, and UWMA time-weighted charts — with WECO, Nelson, and Montgomery detection rules, phases for before-and-after comparison, and stratification by operator, shift, machine, or any factor.

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Microsoft Excel with the Analyse-it tab selected, showing the Control section of a process control report for copper concentration in a plating pool: the Xbar chart and R chart with 3-sigma limits across the IQ, OQ and Production phases, the out-of-control points in the IQ phase flagged and annotated, the points coloured by operator, the Montgomery rules line, and the Process Control task pane open on Control Chart (Shewhart) with the chart type and the rule set table. Handwritten notes: Runs inside Excel: every analysis is on the Analyse-it tab; Control charts and capability: two groups on the tab; Xbar and R charts across three phases, each with its own limits; signals labelled with the cause; Phase, colour by factor, point labels; The report is an ordinary Excel worksheet: share it, archive it, open it on any PC with Excel.

Every chart type, every detection rule, in one package

Excel has no control chart. A line chart with limit lines drawn by hand plots the data and stops: no detection rules, no phases, no time-weighted charts, no attribute charts. Runs, trends and oscillation patterns are left to the eye. Dedicated SPC tools often cover part of the picture — Shewhart charts but not time-weighted charts, CUSUM but not attribute charts. Quality teams stitch together several tools, transfer data between them and lose continuity between charting and investigation.

Is the process stable, or is a small sustained shift building that no single point outside the limits will show? Did the new supplier, the revised procedure or the recalibrated equipment move the process? Is one operator, shift or machine behind the variation?

Xbar-R, Xbar-S, Xbar, R, S, I-MR, I and MR Shewhart variable charts

The chart should match the subgroup size and the structure of the data. Xbar-R for subgroups of 2–8, Xbar-S for larger subgroups, I-MR for individual measurements, or a single Xbar, R, S, I or MR chart on its own. Plot the points as point, line, high-low or box plot.

  • Xbar-R
  • Xbar-S
  • Xbar
  • R
  • S
  • I-MR
  • I
  • MR
  • Levey-Jennings chart
  • Plot styles: point, line, high-low, box plot
Microsoft Excel showing the Control section of a process control report for loan processing costs: the Individual chart and the Moving range chart with 3-sigma limits across phases I and II, the out-of-control points at observations 39 and 40 flagged, and the Process Control task pane open on Control Chart (Shewhart) with the chart type I-MR. Handwritten notes: Individuals chart with the known mean and 3-sigma limits; two phases; Moving range chart beneath; Chart type, and known process parameters.
I-MR chart of loan processing costs across two phases: the individual values and the moving range, with three out-of-control signals at observations 39 and 40.

p, np, c and u Shewhart attribute charts for defectives and defects

Pass/fail inspection results and defect counts need attribute charts, not variable charts. p and np chart the proportion or count of defective units in a sample; c and u chart the number of defects per unit or per inspection. The same detection rules, phases and stratification apply as for variable charts.

  • p
  • np
  • c
  • u
Microsoft Excel showing the Control section of a process control report for nonconforming purchase orders: the p chart with 3-sigma limits that change with the subgroup size, sample 11 flagged, the out-of-control signals table, the process parameters and the control limits for each subgroup size beneath, and the Process Control task pane open on Control Chart (Shewhart) with the chart type p. Handwritten notes: p chart: the control limits step with the subgroup size; Centre and limits for each subgroup size; Varying sample size; Chart type: p, np, c or u.
p chart of nonconforming purchase orders in subgroups of 80 to 120 units: the control limits change with the subgroup size, and sample 11 is flagged.

CUSUM, EWMA and UWMA time-weighted charts for small sustained shifts

Shewhart charts detect large, sudden shifts; a reagent degrading gradually or a tool wearing over time does not produce one. CUSUM (cumulative sum), EWMA (exponentially weighted moving average) and UWMA (uniformly weighted moving average) charts accumulate the evidence of a small, persistent change in the process mean.

  • CUSUM (cumulative sum), standardised or in the original units
  • EWMA (exponentially weighted moving average)
  • UWMA (uniformly weighted moving average)
Microsoft Excel showing the Control section of a process control report for copper concentration: the EWMA chart with weight 0.2 and 3-sigma limits across the OQ and Production phases, the out-of-control point on 23/01 flagged, the R chart beneath, and the Process Control task pane open on the EWMA chart section. Handwritten notes: EWMA chart across the phases, with the signals flagged; R chart beneath; EWMA: weight lambda and limit width L.
EWMA chart (λ = 0.2, L = 3) of copper concentration with the R chart beneath, across the OQ and Production phases: one signal on 23/01.

WECO, Nelson, Montgomery and custom detection rules

A point outside the limits is the easiest signal to see; runs, trends and oscillation are not. Apply the WECO, Nelson or Montgomery rule set, or define custom rules, on any chart. Points beyond the control limits, runs above or below the centre line, trends, stratification and oscillation patterns are flagged on the chart without manual inspection. The out-of-control signals table lists each signal with its phase, date, statistic, value and the rule broken. Label the out-of-control points directly on the chart for reporting and investigation.

  • WECO rules
  • Nelson rules
  • Montgomery rules
  • Custom rules
  • Label out-of-control points
Microsoft Excel showing the out-of-control signals of a process control report for copper concentration: the Montgomery rules line, the table of seven signals in the IQ phase with the date, statistic, value and rule broken for each, the rule descriptions, the process parameters and control limits for each phase beneath, and the Process Control task pane open on Control Chart (Shewhart) with the rule set table. Handwritten notes: Out-of-control signals: phase, date, statistic and the rule broken; Process parameters by phase: known or estimated; Rule set: WECO, Nelson, Montgomery or custom.
Seven out-of-control signals in the IQ phase of the Xbar-R chart, each listed with its date, statistic, value and the Montgomery rule broken, and the rule set in the task pane.

Phases with separate control limits, and stratification by any factor

A process change — a new supplier, a revised procedure, recalibrated equipment — should not have its limits pulled by historical data. Set a new phase and each period gets its own control limits, calculated from the data or specified from a known standard. The effect of the change shows directly on the chart. Stratify by operator, shift, machine, material lot or any factor, and the points are coloured by that factor. Patterns hidden in aggregate data — one operator consistently above the centre line, greater variability on a particular shift — become visible.

  • Phases with separate control limits per period
  • Control limits from data or specified standard
  • k-sigma or probability (α) control limits
  • Zones A, B, C and standardised charts
  • Stratification by any factor (colour points)
Microsoft Excel showing the Control section of a process control report for copper concentration: the CUSUM chart with k 0.5 and decision limits h 5 across the OQ and Production phases, the R chart beneath, the process parameters for each phase with the mean and sigma marked as known or estimated, and the Process Control task pane open on the CUSUM chart section. Handwritten notes: CUSUM chart across the phases, with its decision interval h; CUSUM: k and h; Parameters by phase: known or estimated.
CUSUM chart (h = 5, k = 0.5) with the R chart beneath, across the OQ and Production phases, and the mean and sigma for each phase: estimated from the data in OQ, specified as known in Production.

Example analyses

See control chart output in detail — Shewhart, CUSUM, EWMA, and attribute charts with detection rules, phases, and stratification — using real datasets you can download and follow along with.

Control Example 1 Shewhart, EWMA and CUSUM
Copper concentration in a plating pool. Three reports on one dataset across the IQ, OQ and production phases. Xbar-R with Montgomery rules and points coloured by operator, flagging seven signals; then EWMA with λ = 0.2, flagging eight; then CUSUM with h = 5 and k = 0.5, flagging eleven.
Control Example 2 Individual and moving range
Loan processing costs. Montgomery, page 268. 40 observations over two phases with a known mean and sigma. I-MR chart with ±3 sigma limits, flagging observation 39 on both the individual and the moving range.
Control Example 3 u chart
Supply chain errors per unit. Montgomery, page 325. 20 samples of 50 units. u chart with ±3 sigma limits around a process mean of 0.074 errors per unit. No out-of-control signals.
Control Example 4 p chart and standardised p chart
Nonconforming purchase orders. Montgomery, page 311. 25 samples of varying size. A p chart whose limits move with the sample size, and the same data as a standardised Z-score chart with fixed ±3 limits. Sample 11 is out of control on both.

Part of the Quality Control & Improvement edition

Control charts are one part of the complete SPC and improvement toolkit. The Quality Control & Improvement edition also includes process capability analysis (Cp, Cpk, Pp, Ppk, Cpm, Z-benchmark) and Pareto analysis, plus the full Standard edition with hypothesis tests, ANOVA, and regression for root cause investigation. See everything in the Quality Control & Improvement edition →

Related guides in our Learn section: which control chart do you need, reading out-of-control signals, and Levey–Jennings charts explained.

Validated, reliable, trusted for nearly 30 years

Validated calculations Every statistic tested against published datasets and thousands of internal test-cases. No reliance on Excel’s built-in functions — Analyse-it handles all calculations internally. See how we develop and validate Analyse-it →
Data stays on your PC No cloud processing, no uploads, no third-party access. Your data never leaves your computer — essential when working with proprietary process data, customer specifications, or regulated production records.
Standard Excel workbooks Charts and results are ordinary Excel workbooks. Share with colleagues, send to auditors or customers, archive for quality records — no Analyse-it licence required to view.
No formulas to break Results contain no formulas, so they cannot be accidentally edited or corrupted. The control chart you reported will be exactly what you find when you reopen the workbook.

Free trial and pricing

Try it on your own data first. The 15-day trial is every feature from all five editions, with no sign-up and no licence key — install it and start straight away.

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Quality Control & Improvement edition from US$ 290 per year, or US$ 760 for a perpetual licence. Every purchase carries a 30-day money-back guarantee. Need a quote for purchasing? Add the licence to the cart and save it as a PDF quote.