Control charts
Set up, run, and review this analysis in Lifescio.
Supported analysis
Choose I–MR for individuals, X-bar/S for rational subgroups, p or np for defective items, and c or u for defect counts. The app calculates three-sigma limits and identifies points outside them. The denominator for p/np/u must describe each sample’s opportunities.
Supported scope: Chart selection must match continuous, binary or count data. Independence and suitable binomial/Poisson variation matter; autocorrelation and overdispersion distort limits. The app flags three-sigma violations, not every possible run-rule pattern.
Prepare data and configure the analysis
Keep observations in time order. For I-MR, the first column contains individual measurements. For Xbar-S, each row is a subgroup of at least two measurements. For p or np, enter defective count and integer sample size; np requires the same sample size in every row.
For c, use defect counts with a constant opportunity basis. For u, enter defect count and positive exposure/opportunity. Counts must be nonnegative integers; defectives cannot exceed sample size. Select the chart type before checking the imported table's column meaning.
Input reference (2 fields)
Enter your data and prespecified choices. Ranges include both limits. For table fields, use cell editing, Paste data, or Import CSV / TSV. Review whether the first imported row contains headings and map the source columns before applying the import. Empty numeric cells are not treated as zero. Open file is for an exported Lifescio analysis JSON file, not a spreadsheet.
| Input | Format | Allowed range | Guidance |
|---|---|---|---|
| Chart type | Selection | — | Choices: I-MR, Xbar-S, p, np, c, u. |
| Process observations | Table | — | I-MR and c use column 1; p, np and u use both columns. Xbar-S uses each row as a subgroup. Columns in order: Observation / count; Sample size / exposure. |
Run and review
- Give the analysis a descriptive name and review every example value. Record units, data preparation, and planning assumptions in Reproducibility & notes. For simulations, record the seed and replication or sampling settings.
- Choose Run analysis. Resolve input errors before interpreting output. In the connected app, a run uses a saved input revision; local preview runs need the page to stay open.
- Review Diagnostics for method limitations, warnings, and available numerical checks. A completed run means computation finished; it does not establish that the assumptions fit your study.
- Use the Result table selector to inspect each output. Editing inputs does not recalculate existing results: an earlier-input notice means you need to run again to obtain matching results.
Understand the outputs
The main control-chart table lists the statistic, center, limits, and whether each point is outside them. I-MR also supplies Moving ranges; Xbar-S supplies a Subgroup S chart table. Review those secondary variation outputs as well as the main plot.
Limits are estimated from all supplied data. Only the three-sigma point rule is applied. A row labeled Within limits does not mean that runs, trends, autocorrelation, or specification compliance have been assessed.
Troubleshooting and common mistakes
If np rejects the data, check whether sample sizes vary; a p chart may match that design. If defectives exceed sample size, distinguish multiple defects from defective items and verify the denominator.
Zero moving-range variation can make I-MR uninformative. Repeated artificial values or sorted measurements destroy the intended time sequence. Do not remove an out-of-limit point without investigating and documenting its cause, and do not read missing run-rule flags as evidence of stability.
After correcting inputs, run again and check that the results belong to the new input snapshot. Increasing simulation draws improves numerical precision only; it does not repair invalid data or an unsuitable model.
Save, compare, and export
In the connected app, Save analysis retains the inputs in your account. Run history lets you inspect earlier runs, each with the input revision it used. In local preview, Save analysis downloads an input file instead; download results before leaving the page.
Use Result + inputs for a JSON archive containing the completed result and its inputs, Download CSV for the selected result table, PDF report for a report, and a chart's SVG button for its figure. Table displays round to three decimals; CSV and JSON exports retain calculation precision. Use those values when assessing a result near a decision boundary.
To reopen an archive, select the matching analysis method and choose Open file. Imported inputs start a new draft; a result archive can also display its retained result. It does not attach itself to an existing account analysis or recompute the result. Save or run the imported draft when you want a new account record.