Performance Metrics
. Performance Metrics: purpose
What are the ways you can measure how successful your Six Sigma project has been in improving quality or decreasing the number of defects?
Before we go into the metrics and definitions, let’s say what “defects” and “defective” mean. Something has a defect if the result or outcome of a process is not what is expected. Something went wrong. The product may still be usable: a car with chipped paint can still be driven.
So some engineers use “defective” to mean a product which is not usable. Oops, we forgot to put an engine in that car: well, that’s a defective car because it can’t be driven. However, for the purpose of quality control, “defective” simply means “contains a defect,” whether that defect is cosmetic or whether it actually affects the function of the part as intended. (So just be careful to make sure you are on the same page in terms of your definition as those you are communicating to).
There can be different types of defects in a single part based on different causes.
B. Performance Metrics–Definitions
Here is a list of the Performance Metrics which are spelled out and then given an acronym if one is commonly used. The description is given of what this metric means. | Performance Metric | Description | 1. | Percentage Defective | What percentage of parts contain one or more defects? | 2. | Parts per Million (PPM) | What is the average number of defective parts per million? This is the same figure in metric 1 above of “percentage defective” multiplied by 1,000,000. | 3. | Defects per Unit (DPU) | What is the average number of defects per unit? | 4. | Defects per Opportunity (DPO) | What is the average number of defects per opportunity? (where opportunity = number of different ways a defect can occur in a single part | 5. | Defects per million Opportunities (DPMO) | The same figure in metric 3 above of defects per opportunity multiplied by 1,000,000 | 6. | Rolled throughput yield (RTY) | The yield stated
What are the ways you can measure how successful your Six Sigma project has been in improving quality or decreasing the number of defects?
Before we go into the metrics and definitions, let’s say what “defects” and “defective” mean. Something has a defect if the result or outcome of a process is not what is expected. Something went wrong. The product may still be usable: a car with chipped paint can still be driven.
So some engineers use “defective” to mean a product which is not usable. Oops, we forgot to put an engine in that car: well, that’s a defective car because it can’t be driven. However, for the purpose of quality control, “defective” simply means “contains a defect,” whether that defect is cosmetic or whether it actually affects the function of the part as intended. (So just be careful to make sure you are on the same page in terms of your definition as those you are communicating to).
There can be different types of defects in a single part based on different causes.
B. Performance Metrics–Definitions
Here is a list of the Performance Metrics which are spelled out and then given an acronym if one is commonly used. The description is given of what this metric means. | Performance Metric | Description | 1. | Percentage Defective | What percentage of parts contain one or more defects? | 2. | Parts per Million (PPM) | What is the average number of defective parts per million? This is the same figure in metric 1 above of “percentage defective” multiplied by 1,000,000. | 3. | Defects per Unit (DPU) | What is the average number of defects per unit? | 4. | Defects per Opportunity (DPO) | What is the average number of defects per opportunity? (where opportunity = number of different ways a defect can occur in a single part | 5. | Defects per million Opportunities (DPMO) | The same figure in metric 3 above of defects per opportunity multiplied by 1,000,000 | 6. | Rolled throughput yield (RTY) | The yield stated