Trending and analysis
Control charts, capability and Generated charts
Trend process and analytical results on an individuals and moving range chart, with alert limits at 2 sigma, action limits at 3 sigma, run rules, specification lines and process capability, then save the chart for routine trending on your dashboard.
In the portal: /app/charts
Make a control chart
Ask Q Intelligence in plain words, for example: "Make a control chart of the assay results in the attached file, with specification 95.0 to 105.0, and tell me which rules are violated." The chart appears in the conversation and Q Intelligence interprets it.
- From an attached file: CSV, text or Excel (.xlsx). Name the column; for a workbook, name the sheet (otherwise the first sheet with numbers is used). The first text column (lot, batch, date) labels the points.
- From a signal review: name the SIG record; its series, specification and target are used.
- From values in the question: paste or type the results in the order they were produced.
- Without Q Intelligence: open Generated charts and choose New chart from data, then paste one result per line, or a table copied from Excel.
Up to 1,000 results are charted; with more, the most recent 1,000 are used and the chart says so.
- Person
1. Attach or paste the data
CSV, Excel, values or a SIG record
- Person
2. Ask for the chart
Name the column, specification and rules
- AI drafts
3. Chart and interpretation
Limits, rules fired, capability, normality
- Person
4. Adjust the settings
Specification, reference lines, baseline, rule set
- Person
5. Save to Generated charts
- Person
6. Show on my dashboard
Trending section, up to 12 charts
- Person
7. Add new results
Limits and rules recomputed every time
- A point beyond an action limit, or a run rule: decide under your SOP whether it needs a deviation or an investigation. The chart flags; people decide.
Reading the chart
| Line | Definition |
|---|---|
| Centre line | Mean of the results the limits are based on |
| Sigma | Average moving range ÷ 1.128 (default), or the sample standard deviation |
| Alert limits | Centre line ± 2 sigma |
| Action limits | Centre line ± 3 sigma |
| Moving range limit | 3.267 × average moving range |
| Specification and target | As given, drawn separately from the statistical limits |
Limits come from all results by default, from a baseline (the first N results, later results judged against them), or from an approved historical mean and sigma. Fewer than 20 results for the limits are flagged as preliminary.
| Code | Rule | Nelson | Western Electric |
|---|---|---|---|
| N1 / WE1 | One point beyond an action limit (3 sigma) | Yes | Yes |
| ALERT | One point beyond an alert limit (2 sigma) | Yes | Yes |
| N2 / WE4 | Run on one side of the centre line | 9 points | 8 points |
| N3 | 6 points steadily increasing or decreasing | Yes | No |
| N4 | 14 points alternating up and down | Yes | No |
| N5 / WE2 | 2 of 3 points beyond 2 sigma, same side | Yes | Yes |
| N6 / WE3 | 4 of 5 points beyond 1 sigma, same side | Yes | Yes |
| N7 | 15 points within 1 sigma | Yes | No |
| N8 | 8 points beyond 1 sigma, both sides | Yes | No |
| MR | A moving range above its limit | Yes | Yes |
| SPEC | A result outside specification | Yes | Yes |
Tip: "In statistical control" and "within specification" are different questions. The chart reports them separately: a process can be in control and still produce results outside specification, and the reverse.
- Markers: out of specification is a red square, beyond an action limit a red dot, beyond an alert limit an amber triangle, a run rule an orange ring; the legend explains each.
- Point at the chart to see each result's value, its distance from the centre in sigma, its moving range and the rules it is part of.
- The Table tab lists every result; CSV downloads the results with limits and rules, PNG the chart image.
Specification and reference lines
- Step 1: Open Specification and limits on the chart.
- Step 2: Set or change the lower and upper specification limits (LSL, USL) and the target. Each is drawn on the y-axis, results outside specification are flagged and capability updates at once.
- Step 3: Add up to six named reference lines (an internal limit, a release claim).
- Step 4: Choose where the control limits come from (all results, a baseline of the first N, or a historical mean and sigma), the sigma method and the rule set.
- Step 5: In a Q Intelligence answer, choose Save to Generated charts to keep the changes.
Process capability
The Capability tab needs at least one specification limit.
| Index | Formula | Meaning |
|---|---|---|
| Cp | (USL − LSL) / 6σ within | Potential capability, if centred |
| Cpk | min(CPU, CPL) | Potential capability, allowing for centring |
| Pp, Ppk | As Cp and Cpk, with the overall standard deviation | Actual performance |
| Cpm | (USL − LSL) / 6 √(σ² + (mean − target)²) | Allowing for distance from target |
Cpk of 1.33 or more is reported as capable, 1.00 to 1.33 marginal, below 1.00 not capable; follow your own SOP where it sets other criteria. The tab shows the histogram with fitted normal curves, expected ppm outside specification and the observed count, with caveats when the process is out of control, has fewer than 30 results, or overall variation is well above within variation.
The Normality tab tests the results with Shapiro-Wilk and Anderson-Darling (see Data analysis); capability indices and ppm assume normal data.
Generated charts and the dashboard
- Charts belong to the organization. Everyone can open them; the person who saved a chart, or an administrator, can change or archive it.
- Routine trending: open a chart and choose Add new results as results come in. A chart made from a signal review can be refreshed from it.
- No silent overwrites: a save made after someone else's newer change is refused; reload and save again.
- Dashboard: Show on my dashboard adds a chart to the Trending section of your Q Dashboard, up to twelve, in an order you choose. Each person chooses their own.
- Recomputed every time: a saved chart stores its results and settings; limits, rules and capability are recomputed whenever it is shown.
- General charts (line, bar, Pareto, histogram, box, scatter) and FMEAs are saved and pinned the same way.