A Moving Average Control Chart For The Sample Mean Based On A Robust Estimator Of Scale
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Date
2009-04
Authors
Jamel, Suffiah
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Abstract
Lately, the use of quality control charts is becoming more important. Many industries
have given increased emphasis on using control charts, such as the Shewhart charts in
the monitoring of manufacturing processes. In this area, however, there are still many
aspects that need to be extended, generalized and improved upon. The traditional
Shewhart control charts are easily affected by occasional outliers that might be a natural
part of a process. The limits of these charts are easily stretched by the presence of
outliers, making them insensitive in the detection of any out-of-control signal. A robust
moving average (MA1oR) chart will be proposed in this dissertation to overcome this
problem. The performance of the proposed chart is compared with that of the
conventional moving average (MA) chart for the process mean using a simulation
study. A moving average control chart is a time weighted chart based on a simple,
unweighted moving average of interest, where the chart's statistics incorporates past
sample points. The simulation study shows that the proposed MAIQR control chart
provides superior results to that of the conventional MA chart in the detection of
outliers and other forms of out-of-control situations when outliers are present.
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Keywords
Mathematics , Quality control -- Charts, diagrams, etc