How do specification limits differ from control limits?

Specification limits and control limits serve different purposes in quality management and process control. Specification limits are defined based on customer requirements or regulatory standards, indicating the acceptable range of variation for a product or service. They represent the maximum and minimum thresholds that a product must meet to satisfy customer needs or legal requirements.

Control limits, on the other hand, are statistical boundaries used within control charts to monitor process stability and performance over time. They are calculated based on the data collected from a process to determine how much variation is normal when the process is under control. Essentially, control limits help identify whether the process is stable or if variations are due to special causes that need investigation.

The correct statement emphasizes that specification limits allow for the detection of values beyond the specified thresholds, indicating when a product may be outside acceptable quality levels. In contrast, control limits are used to monitor the variability of the process itself rather than to determine pass or fail status concerning specifications. This distinction is crucial: while specification limits inform whether a product is suitable for market release, control limits help ensure that the process producing the product remains consistent and capable of meeting those specifications.