In quality management, inspections are essential to verify that products or materials meet defined specifications. However, inspecting every single item in large batches can be time-consuming and costly. This is where statistical sampling comes into play—allowing organizations to inspect a representative subset of items while maintaining confidence in quality levels. Within the SAP Quality Management (QM) module, statistical sampling procedures are embedded to optimize inspection processes and ensure efficient resource utilization.
Statistical sampling is a technique where a subset (sample) of items is selected from a larger population (lot or batch) to infer the quality of the entire lot. The sample size and acceptance criteria are determined based on statistical principles to balance inspection costs against the risk of accepting defective products.
SAP QM incorporates statistical sampling methods to:
- Reduce inspection effort and cost without compromising quality.
- Provide objective and repeatable inspection results.
- Facilitate compliance with industry standards such as ISO 2859 (ANSI/ASQC Z1.4).
- Enable effective decision-making on lot acceptance or rejection.
- Lot Size: Total number of units in the batch to be inspected.
- Sample Size: Number of units selected from the lot for inspection.
- Acceptance Number: Maximum number of defective units allowed in the sample for the lot to be accepted.
- Inspection Level: Degree of rigor in the sampling plan (e.g., general, tightened, or reduced).
- AQL (Acceptable Quality Level): Maximum percentage of defective items considered acceptable.
In SAP QM, sampling procedures specify how to determine sample sizes and acceptance criteria based on lot size and inspection level.
- Configured via Transaction Code QA32 or through customization in SPRO under Quality Management → Quality Inspection → Sampling Procedures.
- Includes standard sampling procedures such as single sampling plans (ISO 2859), double sampling, or sequential sampling.
Sampling procedures are linked to inspection plans, which define the characteristics to be inspected.
- When an inspection lot is created, SAP automatically applies the relevant sampling procedure.
- The system calculates sample size and acceptance number dynamically.
¶ 3. Creating Inspection Lots and Sampling Execution
- Upon goods receipt or production confirmation, an inspection lot is generated.
- Inspectors perform measurements on the sample size specified by the statistical plan.
- Results are recorded in SAP QM via transactions like QA32 or QE51N.
Based on the inspection results:
- If the number of defects ≤ acceptance number → lot is accepted.
- If defects exceed acceptance number → lot is rejected or subjected to further action.
SAP QM supports automatic lot status updates and workflows for rework, scrapping, or supplier notification.
- Efficiency: Focuses inspection efforts on representative samples rather than 100% inspection.
- Cost-Effectiveness: Reduces inspection time and labor costs.
- Objectivity: Uses statistically valid criteria reducing human bias.
- Flexibility: Allows adjustment of inspection rigor based on product criticality or supplier history.
- Compliance: Meets international quality standards for sampling.
- Define clear sampling policies aligned with business goals and risk tolerance.
- Train quality personnel on statistical sampling concepts and SAP QM transactions.
- Regularly review and adjust sampling plans based on historical defect rates and process capability.
- Integrate sampling results with quality analytics for continuous improvement.
Statistical sampling is a cornerstone of effective quality inspection in SAP Quality Management. By leveraging SAP QM’s sampling procedures, organizations can strike a balance between thorough quality checks and operational efficiency. This ensures that only products meeting quality standards progress in the supply chain—protecting brand reputation and customer satisfaction.