Page 230 - The Six Sigma Project Planner

Table 19. Methods of Evaluating Attribute Inspection

True Value Method of Evaluation Comments
Expert Judgment: • Metrics:
An expert looks at the Percent correct
classifications after the
• Quantifies the accuracy of the
operator makes normal classifications.
classifications and decides
which are correct and which • Simple to evaluate.
are incorrect. • Who says the expert is correct?

• Care must be taken to include all types of
attributes.
• Difficult to compare operators since
different units are classified by different
people.

• Acceptable level of performance must be

decided upon. Consider cost, impact on

customers, etc.
Round Robin Study: • Metrics:
Known
A set of carefully identified 1. Percent correct by inspector
objects is chosen to represent 2. Inspector repeatability
the full range of attributes. 3. Inspector reproducibility
1. Each item is evaluated by 4. Stability
an expert and its condition 5. Inspector “linearity”
recorded.
• Full range attributes included.
2. Each item is evaluated by
every inspector at least • All aspects of measurement error
twice. quantified.
• People know they’re being watched, may
affect performance.

• Not routine conditions.
• Special care must be taken to ensure rigor.

• Acceptable level of performance must be

decided upon for each type of error.

Consider cost, impact on customers, etc.

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