Process Metrics

Process metrics need to lead to the most appropriate behaviors. Processes have variability and may or may not have specifications.

Performance measurements for processes need to provide direction to the most appropriate behaviors considering both process variability and any specification that may exist. The output of processes can have both common-cause variability and special-cause variability.

In process metric reporting, typical process variability is separated from unusual events or trends. Traditionally this separation is make using statistical process control (SPC) charts such as x-bar and R charts and p-charts. How a process is performing for an in-control process relative to specifications traditionally involves techniques such as process capability indices.

However, traditional control charting and process capability reporting have mathematical issues. An Integrated Enterprise Excellence (IEE) 30,000-foot-level reporting format addresses these issues. IEE 30,000-foot-level reporting provides both a process stability assessment and predictive statement for stable processes in one chart.

Process Capability Analysis – A Better Way

Performance Measurements, Process Metrics /

For a given process, do you think everyone would create a similar looking control chart and make a comparable statement relative to its control and capability? Not necessarily. Process statements are not only a function of procedural characteristics and sampling chance differences but can also be very dependent upon sampling approach. The implication of this is that one person could describe a process as being out of control, which would lead to activities that immediately address process perturbations as abnormalities, while another person could describe the process as being in control. For this second interpretation, the perturbations are perceived as fluctuations typically expected within the process, where any long-lasting improvement effort involves looking at the whole process. During this session, issues with traditional control charting techniques (e.g., x-bar and R charts) and process capability indices statements (e.g., Cp, Cpk, Pp, and Ppk) will be discussed. An enhanced alternative predictive performance measurement system will then be described that not only provides resolution to these issues but can also provide a predictive statement, which everyone can understand.

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Enhanced Approach for How to Show Process Improvement

Performance Measurements, Process Metrics /

With a high-level process-output tracking at the 30,000-foot-level, there will be an infrequent subgrouping/sampling plan such that the typical variability from input variables that could affect the response will occur between these subgroupings. An infrequent subgrouping/sampling interval could be day, week, or month, where responses from differing people, departments, machines, and so forth would be captured within each subgroup. 30,000-foot-level charting does not offer timely identification of process changes but instead provides a high-level view of how the process is performing from a customer-of-the-process point of view.

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Enhanced Attribute Data Control Chart with Process Capability Statement

Performance Measurements, Process Metrics /

Attribute, pass/fail proportion data, can be monitored over time for stability and then, when a process is stable, provide a prediction statement. When a process has a recent region of stability, it can also be said to be predictable. When this occurs, we can use historical data to make a statement about what we might expect in the future, assuming things stay the same; e.g., the center line of the chart if no transformations are needed to create the 30,000-foot-level chart, and the subgroup sizes are approximately the same.

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Enhanced SPC P-chart can Include Capability Statement in One Chart

Performance Measurements, Process Metrics /

An enhanced  Statistical Process Control SPC p-chart approach provides in one chart both a process stability and capability assessment/statement. The Integrated Enterprise Excellence (IEE) enhanced SPC p-chart 30,000-foot-level measurement approach for non-conformance rate time-series tracking of data (i.e., from a high-level overall process output point of view) also provides a prediction statement when a process

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