Cause-and-Effect Diagrams
An important aspect of process productivity or quality analysis is linking each metric of required performance dimension (attribute) to the inputs, methods, and process steps that build a particular attribute into the service or product. One way of investigation is to develop a cause-and-effect diagram that relates a key performance problem to its potential causes. It was first proposed by Kaoru Ishikawa. The diagram helps the analyzing team to think about the possible causes in the process/operations involved. Inputs or activities that have no bearing on a particular problem are not shown on the diagram.
The cause-and-effect diagram is also called a fishbone diagram. The main performance gap is shown at the fish’s “head,” the major categories of potential causes as structural “bones,” and the likely specific causes as shown as “ribs.” When constructing the diagram, an analyst identifies all the major categories of potential causes for the problem. These might be personnel, machines, materials, operations, and methods of the process. For each major category, the analyst teams identifies all the likely causes of the performance gap. For example, under personnel might be listed “lack of training,” “poor communication,” and “absenteeism.” Creative thinking supported knowledge (updated objective and explicity knowledge and implicit knowledge based on experience) in each category identified helps the analyst team to identify and properly classify all suspected causes. The team then systematically investigates the causes listed on the diagram for each major category, updating the chart as new causes become apparent. The process of constructing a cause-and-effect diagram calls managers, engineers and operator attention to the primary factors affecting process failures.
Op Management, Krajewski.
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