Quality Quiz from Professor Cleary
"B" is correct.
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Karmond Geeya, by disregarding one of the essential assumptions, is rendering the use of c-charts invalid. All of the four assumptions must be met. These assumptions are:
- The occurrences of a defect type are discrete;
- The area of opportunity (motor) is well defined;
- The occurrence of one type of defect is not influenced by the occurrence of another type;
- The probability of any one type of defect occurring is small.
Although assumption #3 is somewhat subjective, Geeya is incorrect in disregarding it. Without all four assumptions in place, she will produce an inaccurate (possibly poisonous) chart.
Below is an example of a c-chart that has met all of the conditions outlined in the four assumptions.
Click to enlarge
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