Explore the Quality Glossary
Accept / Reject Criteria
Standards used to determine whether a product or service meets required quality expectations. These criteria may include technical specifications, contractual requirements, or performance benchmarks. Each product or process should have measurable acceptance limits, and routine checks should be performed to ensure compliance and consistent performance.
Acceptable Quality Level (AQL)
The maximum defect level considered acceptable during continued production or shipments. AQL ensures that product quality remains within agreed-upon limits over time.
Acceptance Number
The highest number of defects allowed within a sample before a lot is rejected. If defects exceed this limit, the batch fails and corrective action is required to address process issues.
Acceptance Sampling Plan
A structured sampling method used to evaluate product quality and decide pass/fail status. May include single, double, sequential, chain, or skip-lot sampling based on production needs and quality requirements.
Adequacy of Standards
The effectiveness of a measurement standard in verifying accuracy of tools and inspection equipment. Ideally, standards should be traceable to national or recognized metrology institutions to ensure reliability and accuracy.
Affinity Diagramming
A method for grouping ideas or data into meaningful categories based on common themes. Useful for organizing brainstorming results and identifying patterns in qualitative information.
Agile Manufacturing
A flexible production approach enabling rapid design, customization, and delivery of high-quality products without compromising cost efficiency or environmental responsibility.
Analysis of Means (ANOM)
A statistical tool used during testing and experimentation to evaluate differences in process performance and identify improvement opportunities.
Analysis of Variance (ANOVA)
A technique used to analyze the sources of variation in a process, determine their significance, and minimize inconsistencies in product output.
Average Outgoing Quality (AOQ)
The maximum expected defect rate leaving a facility after inspection. AOQ ensures defective units remain within acceptable levels and may require full inspection if defects rise.
Audit (Quality)
An independent review that compares actual performance against defined standards to verify compliance and identify areas for improvement.
Average Run Length (ARL)
The expected number of samples taken before a control chart signals a process shift. ARL is used to evaluate effectiveness of statistical monitoring systems.
Batch
A specific, uniform quantity of product produced under the same conditions and controlled as a single unit for quality evaluation.
Bathtub Curve
A reliability model showing three phases of failure: early failures, consistent mid-life performance, and increased failures at end of life. Common in product lifecycle analysis.
Bimodal Distribution
A data distribution with two peaks, indicating two dominant influences or populations affecting process data.
Calibration
Comparing a measurement instrument to a known standard to verify accuracy, identify error, and ensure reliability.
Process Capability Index (Cp)
A measure comparing process variation to specification limits, determining whether a process can consistently produce within required tolerances.
Causal Analysis
A method used to identify root causes of defects or failures and implement corrective actions to prevent recurrence.
Continuous Sampling Plan
A quality strategy for continuous production systems. Starts with 100% inspection, reduces sampling after consistent quality is proven, and returns to full inspection when defects reappear.
Control Chart
A statistical graph used to monitor process behavior over time, detect variations, and determine when corrective action is required.
Control Chart Factor
A statistical value used to calculate control limits when constructing X-bar and range control charts.
Cost of Poor Quality (COPQ)
Total financial loss caused by defects and quality failures. Includes:
Internal costs: scrap, rework, waste, labor, admin time
External costs: recalls, warranty claims, returns, legal action, reputational damage
Early supplier audits and proactive quality systems significantly reduce COPQ by preventing failures before they occur.
Cost of Quality (COQ)
The total cost associated with ensuring quality and preventing defects, including prevention measures, process assessments, and financial impact analysis. COQ helps justify and manage quality-related investments.
Critical Defect
A defect considered hazardous, posing potential harm or injury to users or personnel, and requiring immediate attention and corrective action.
Defect
Any condition where a product or service fails to meet customer requirements or specifications. Defects are commonly categorized as critical, major, minor, or low-impact based on severity.
Demerit Chart
A quality tool used to track and evaluate defects in production by assigning weighted values to defect categories (critical, major, minor, etc.), helping analyze trends and drive improvements.
Design of Experiments (DOE)
A structured statistical approach for planning and executing tests to understand process variables and optimize product or process performance.
Double Sampling
An inspection process where an initial sample is tested and, based on results, a second sample may be required to decide whether a lot is accepted or rejected.
Failure Mode & Effects Analysis (FMEA)
A proactive method for identifying potential failure points in materials, components, or manufacturing processes, assessing risk, and implementing preventive measures.
Inspection
The process of measuring, testing, and evaluating product or process outputs against defined standards to ensure conformance in size, function, appearance, and performance.
ISO 9000 Standards
A set of globally recognized quality standards established by ISO. Key certifications include:
• ISO 9001 – Full quality management system from design through service
• ISO 9002 – Covers production and installation processes (no design)
• ISO 9003 – Focuses on inspection and testing activities
Lot Tolerance Percent Defective (LTPD)
A metric comparing defect percentage in a lot to its probability of acceptance — higher defect rates reduce acceptance likelihood.
Lower Control Limit (LCL)
The lowest acceptable value on a control chart; positioned three standard deviations below the process mean.
Minimum Acceptable Quality
The highest allowable level of defects for a product or service to still be considered acceptable during sampling.
Nondestructive Testing (NDT / NDE)
Testing methods that evaluate product integrity without damaging or altering the item being inspected.
np Chart
A control chart used to monitor the number of defective units in samples when the sample size remains constant.
Pareto Chart
A bar chart based on the 80/20 rule, highlighting the most significant factors or defect sources to focus improvement efforts.
Process Quality Audit
A review of process performance and operator practices to confirm compliance with quality standards and identify improvement opportunities.
Q9000 Series
U.S. standards aligned with ISO 9000, covering quality documentation, audit procedures, and system requirements for manufacturing and service organizations.
Quality Control
Activities and procedures used to ensure products or services meet required quality standards and customer expectations.
Quality Engineering
The application of engineering and statistical methods to design, operate, and continually improve processes to minimize defects and variability.
Random Sampling
A method where every unit has an equal chance of being selected, ensuring unbiased sample selection.
Reliability Engineering
The practice of predicting and improving product or system performance to prevent failure and ensure long-term reliability.
Representative Sampling
Selecting samples that accurately reflect the entire lot, minimizing bias and ensuring valid quality conclusions.
Sample
A defined number of items selected from a lot to evaluate whether the entire batch meets quality standards.
Statistical Process Control (SPC)
A set of statistical tools used to monitor process performance, identify variation sources, and maintain control over production quality.
Statistical Quality Control
A broader discipline combining SPC and other statistical techniques to measure and improve quality across processes.
Taguchi Methods
Quality techniques focused on minimizing variation and loss to customers by designing robust processes and products.
Variation
Natural differences that occur in any process or output; managing variation is essential to achieving consistent quality.
Vendor Compliance Audit
Supplier Verification
SS Quality Inspection Report – Comprehensive Supplier Verification Audit SS Quality Inspection Report – Financial Stability and Credit Assessment SS Quality Inspection Report – Initial Supplier Capability Evaluation SS Quality Inspection Report – Supplier Quality and Compliance Audit
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