Some Six Sigma definitions which I’ve collected over time.
| Term | Definition |
| CTQs | Critical To Quality. The sort list of the most important customer wants. |
| Customer | Any internal/external person/organisation who receives the output of a process. |
| Customer Requirements | The needs and expectations of the customer. Which is translated into measurable terms. Used in the process to ensure compliance with customers’ needs. |
| Defect | Any occurrence or instance where the product/service fails to meet the customers requirements. |
| Defect opportunity | A type of potential defect on a unit of throughput/output, which is important to the customer. |
| DPMO | Defects Per Million Opportunities. Calculation used in process improvement initiatives indicating the amount of defects in a process. |
| Sigma | A statistical term that measures how much a process varies from perfection, based on the DPMO. |
| Six Sigma | A level of process performance equalling 3.4 DPMO. |
| Standard deviation | Statistical measure of how much variation there is in a set of data. |
| Variation | Change/fluctuation of a specific characteristic. Determines process stability/predictability. |
