Quality control checks and sampling: control limits, defect rates and sampling plans
For quality inspectors, quality technicians, production team leads and goods-in staff who already read control charts and apply sampling plans, and now need to set them up and judge them. Complete 'Reading control charts' and 'Defects, inspection records and sampling' first. You'll calculate defect rates and p-chart limits, calculate X-bar and R chart limits, apply the Western Electric rules, read an operating characteristic (OC) curve, and weigh 100% inspection against sampling and process control. Methods and worked values come from the NIST/SEMATECH e-Handbook of Statistical Methods. Your site's control plan and disposition authority still decide what happens to product.
- Level
- Intermediate
- Length
- About 95 minutes
- Contents
- 5 lessons · final exam
- Status
- Published · updated 10 Oct 2026
Skills you'll practise
- Calculate a defect rate and p-chart control limits from inspection counts
- Calculate X-bar and R chart control limits from subgroup measurements
- Identify out-of-control signals with the Western Electric rules and decide when control limits should be recalculated
- Read an operating characteristic (OC) curve to judge what a sampling plan will accept
- Choose between 100% inspection, acceptance sampling and process control for a quality check
Course outline
- 1.Calculating defect rates and p-chart control limitsLesson · 18 min
- 2.Calculating X-bar and R chart control limitsLesson · 17 min
- 3.Identifying out-of-control signals and deciding when to recalculate limitsLesson · 17 min
- 4.Reading an OC curve to judge what a sampling plan will acceptLesson · 17 min
- 5.Choosing between 100% inspection, acceptance sampling and process controlLesson · 16 min
- 6.Quality control checks and sampling: control limits, defect rates and sampling plans: knowledge checkKnowledge check · 15 questions
- 7.Quality control checks and sampling: control limits, defect rates and sampling plans: practical exerciseKnowledge check · 1 question
- 8.Final exam10 questions · passing it completes the course, so people who already know the material can test out
Sources it draws on
The lessons and questions are written from these references, so learners can go back to the original.
- NIST/SEMATECH e-Handbook of Statistical Methods, 6.3.1 What are control charts?
- NIST/SEMATECH e-Handbook of Statistical Methods, 6.3.2 What are variables control charts? (control vs specification limits, recalculating limits, WECO rules)
- NIST/SEMATECH e-Handbook of Statistical Methods, 6.3.2.1 Shewhart X-bar and R and S control charts
- NIST/SEMATECH e-Handbook of Statistical Methods, 6.3.3.2 Proportions control charts
- NIST/SEMATECH e-Handbook of Statistical Methods, 6.2.1 What is acceptance sampling?
- NIST/SEMATECH e-Handbook of Statistical Methods, 6.2.2 What kinds of lot acceptance sampling plans (LASPs) are there?
- NIST/SEMATECH e-Handbook of Statistical Methods, 6.2.3.1 Choosing a sampling plan: MIL Standard 105D
- NIST/SEMATECH e-Handbook of Statistical Methods, 6.2.3.2 Choosing a sampling plan with a given OC curve (OC, AOQ and ATI examples)
See it with your own jobs and topics
Tell us about your team and we'll walk you through setup, from choosing jobs to your first skills check.