AAOM Handbook

INTERNAL

AI.04 Produce Capability Histograms Context

A Key Performance Indicator or Control Measure is produced for the purpose of helping us make the decisions necessary to control or improve a process. An appropriate intervention in a process, taken at the right time, can ensure that the performance is maintained or improved. Every un-necessary intervention in a process tends to increase the variation in, and losses produced by, the process. It is therefore essential that only the necessary and appropriate interventions be made. Making the right decision on the need for intervention is dependent on having the right data, and on making the correct interpretation of the data. The Set Performance Targets process established what the Key Performance measures are for each process and the TAs related to Measure Output, Work Management and Social performance defined how these are measured. Control measures are defined through the tools used during the Analyse and Improve process. Statistical analysis tools help us to take the guesswork out of interpretation of the data, and to decide the appropriate and in-appropriate times for intervention in a process. The tools we have used for guiding the decision to intervene in a process thus far are Control charts, from which we can now produce Capability Histograms. Purpose To provide the information necessary for making a decision that intervention in a process is required. Quantity One set of appropriate Control Charts and Capability Histograms for each of the measured variables. Quality The Capability Histogram shall be constructed;  To a common format;  Including only the most current period of representative process performance from the control chart in Capability Histograms,  Excluding validated special (assignable) cause events from the Histogram, and  Using Standardised Capability Tests; o the shape of Histogram matches expectations, o the range of variation is less than the difference between the Specification Limits, o all of the variation lies between the specification limits. Resources This task is the responsibility of the manager of the process.