Moving Average Chart
The points appear to vary randomly around the center line and are within the control limits; however, there are two points that come close to the control limit that you may want to investigate.
A type of time-weighted control chart that plots the unweighted moving average over time for individual observations. This chart uses control limits (UCL and LCL) to determine when an out-of-control situation has occurred. Moving average (MA) charts are more effective than Xbar charts in detecting small process shifts, and are particularly useful when there is only 1 observation per subgroup. However, EWMA charts are generally preferred over MA charts because they weight the observations.
For example, a manufacturer of centrifuge rotors wants to track the diameter of all rotors produced during a week. The diameters must be close to the target because even small shifts cause problems. The following moving average chart resulted.
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Moving Average Chart |
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The points appear to vary randomly around the center line and are within the control limits; however, there are two points that come close to the control limit that you may want to investigate.
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The observations can be either individual measurements or subgroup means. Moving averages are calculated from artificial subgroups that are created from consecutive observations.