LSL = 2.5 USL = 2.687
The lower specification is 2.500 inches and the upper specification is 2.687 inches. Any labels that are smaller than 2.5 inches or larger than 2.687 inches are unacceptable.
Values between which products or services should operate. Specification limits are usually set by customer requirements. For example, you print labels for a shipping process. If the labels are too big or too small, they will not feed into printers properly.
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LSL = 2.5 USL = 2.687 |
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The lower specification is 2.500 inches and the upper specification is 2.687 inches. Any labels that are smaller than 2.5 inches or larger than 2.687 inches are unacceptable. |
Consider a call center where calls must be answered within 30 seconds.
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USL = 30 |
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In this case, only an upper specification is relevant because the quicker a call is answered, the better. |
There may be situations where only one specification limit is appropriate, such as chemical purity. You may require an inert gas to be at least 80% pure, but you set no upper specification limit because purer is better.
Specification limits are different from control limits. Specification limits are based on what is required for proper function or appropriate service. Control limits are calculated from process data. They represent how your process actually performs, while specification limits show the desired performance.
Instead of specification limits, a process may have boundaries. It is possible for a measurement to exceed a specification limit, but it is impossible for a measurement to exceed a boundary. For example, although purer is better, an inert gas cannot exceed 100% purity. Replacing one of your specification limits with a boundary in Minitab yields a one-sided capability analysis.
