The defect rate in Six Sigma is defined as the number of defects divided by the number of opportunities to create defects. (a) Some practitioners define the number of opportunities as the number of inspections and/or tests. Why is this not a valid way to determine defect rate? (Hint: the best manufacturers tend to do very little test and inspection.) (b) Another school of quality thought defines opportunities as value-added transformations. That is, a product or service is changed by the process, the change matters to the customer (i.e., if a step removes scratches from a previous step, it doesn't count), and only first-time operations count (i.e., rework steps are not opportunities). Will this lead to a more reliable measure of defect rate than the previous definition? How might an unscrupulous practitioner manipulate the calculation of opportunities to make the defect rate look better than it actually is?

Step by step solution

01

(a) Validity of defining opportunities as the number of inspections and/or tests

Defining the number of opportunities as the number of inspections and/or tests is not a valid way to determine the defect rate because it doesn't take into account the actual processes involved in creating the product or service. The best manufacturers tend to do very little test and inspection because they have optimized their processes to deliver quality products with minimal defects. In such cases, measuring defect rate solely based on tests and inspections would lead to an inaccurate representation of the actual quality of the product or service.

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(b) Defining opportunities as value-added transformations

Defining opportunities as value-added transformations allows for a more reliable measure of defect rate than the previous definition. This is because it focuses on the actual processes that create changes in the product or service that matter to the customer. By considering only first-time operations and excluding rework steps, this definition encourages the optimization of processes to reduce defects and improve quality. However, an unscrupulous practitioner might manipulate the calculation of opportunities to make the defect rate look better than it actually is. This could be done by deliberately excluding or miscounting certain value-added transformations, or by labeling some defective processes as non-value-added transformations. By doing so, the practitioner artificially reduces the number of opportunities, which in turn, lowers the calculated defect rate, making it appear better than reality.

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