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Overview |
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Definitions |
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Factors for Control charts. |
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Moving average calculations. |
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Exponentially weighted moving average chart calculations. |
Moving averages are generally used to smooth out the noise in a time series and forecast future values of the series.
A MA (Moving Average) chart can be drawn based on either:
Subgroup means or
Individual observations (Subgroup
size =1).
A moving average is calculated by averaging consecutive groups of observations in a series.
Example
A series begins with the numbers 8,9,10,11, and 12 and the moving average length is 3.
The values of the moving average are as follows:
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Value |
Is |
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First |
Missing |
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Second |
Missing |
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Third |
8,9, and 10 |
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Fourth |
9,10, and 11 |
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Fifth |
10, 11, and 12 and so on. |
Terms used in moving average calculations are:
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Subgroup Size |
A set of one or more observations that are used to calculate a value on an SPC chart. Any subgroup size between 1 and 10 can be selected on the Chart tab in the SPC Control Properties dialog box. |
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Length of MA |
Length of the moving averages. The value that is specified will be the number of subgroup means that will be included in each average. Any Length between 1 and 24 can be selected on the Chart tab in the SPC Control Properties dialog box. |
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Weighting Factor |
Weight to be used in the exponentially weighted moving average. The value specified must be a number between 0 and 1. |
Charts
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Exponentially weighted moving average chart calculations. |
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Moving average calculations. |
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Moving range calculations. |
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SPC chart calculations. |
