Calculator Inputs
Example Data Table
| Lot | Outcome | Notes |
|---|---|---|
| 1 | Accepted | Stable start |
| 2 | Accepted | Within control limits |
| 3 | Rejected | Special cause suspected |
| 4 | Accepted | Corrective action applied |
| 5 | Rejected | Triggers tighten rule in 5-lot window |
Formula Used
- Normal → Tightened if RejectsW ≥ Reject Threshold.
- Tightened → Normal if Accept Streak ≥ Tightened Recovery Accepts.
- Normal → Reduced if Accept Streak ≥ Reduced Entry Accepts and production is stable.
- Reduced → Normal if a recent rejection occurs, triggers fire, or stability is off.
How to Use This Calculator
- Select your current inspection state (Normal, Tightened, or Reduced).
- Paste your lot outcomes history using A for accepted and R for rejected.
- Set the window size and thresholds to match your procedure.
- Mark production stability to allow or block Reduced inspection.
- Press Submit to view the recommended next state above the form.
- Export your analysis as CSV or PDF for audits and reviews.
Operational Notes
Inspection Switching in Daily Operations
Switching rules translate acceptance sampling history into a repeatable inspection posture. This calculator summarizes recent lot outcomes, counts rejects inside a rolling window, and measures the acceptance streak. By logging each lot as Accepted or Rejected, supervisors can compare performance against procedures and decide whether to maintain Normal, escalate to Tightened, or allow Reduced sampling. The per-lot table keeps decisions tied to lot numbers.
Using Rolling Windows to Detect Drift
A rolling window focuses attention on the most recent performance, where process drift or supplier variation appears first. By setting the window size to match production cadence, you can compare short runs against longer periods. Common windows range from five to fifteen lots in high-volume lines, while low-volume cells may use smaller windows to stay responsive. The reject threshold acts like a trigger point; once reached, the calculator recommends moving to Tightened inspection to increase detection.
Recovering from Tightened to Normal
Tightened inspection is costly, so recovery criteria should be explicit. The consecutive acceptance requirement represents evidence that corrective actions worked and the process is back in control. Many plans use five consecutive accepts as a baseline, then adjust upward for critical characteristics. This tool reports the current acceptance streak and shows it for every lot in the results table, making it easy to prove when the recovery milestone was met and when Normal inspection resumed.
Entering Reduced Inspection Responsibly
Reduced inspection is appropriate only when performance is stable and risk is understood. The calculator requires both a long acceptance streak and a stability flag, reflecting common procedures that restrict reduced sampling during changes, maintenance, or new operators. Reduced entry criteria often start at ten consecutive accepts, then increase for safety-related parts. If stability is off, the tool blocks reduced recommendations and keeps the decision in Normal where oversight remains stronger and feedback loops stay tight.
Exportable Evidence for Reviews and Training
Quality reviews need traceable evidence, not screenshots. The CSV export provides a clean per-lot record of window rejects and acceptance streaks, ready for trend charts or KPI dashboards. The PDF export produces a shareable report for management reviews, supplier discussions, and operator training. Standardized outputs help build consistent documentation across product lines, support internal audits, and reinforce continuous improvement by showing how parameter changes affect switching decisions over time.
FAQs
What are switching rules in quality control?
They are documented criteria that change inspection intensity based on recent acceptance sampling results, helping teams respond consistently to emerging quality risk.
How do I choose a window size?
Match it to production cadence and feedback speed. High-volume lines often use 5–15 lots, while low-volume processes may use smaller windows to avoid delayed reactions.
What does the reject threshold mean?
It is the number of rejects inside the rolling window that triggers escalation. When rejects meet or exceed the threshold, the tool recommends Tightened inspection.
Why is a stability flag included?
Reduced inspection is normally allowed only when the process is stable. The flag prevents reduced recommendations during changes, maintenance, new setups, or unknown conditions.
Can I use this for audits?
Yes. The results table records per-lot streaks and window rejects, and the CSV/PDF exports provide consistent evidence of why inspection states were changed.
Does this replace an official sampling standard?
No. It supports your procedure by applying your chosen parameters. Always align thresholds and criteria with approved sampling plans, risk assessments, and customer requirements.