Geometric Moving Average Charts

Geometric Moving Average Charts - “WEIGHTED MOVING...

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Unformatted text preview: “WEIGHTED MOVING AVERAGE CHARTS An arithmetic moving average applies equal value to each data point in the average Is this really desired? Generally, it is desired to put more weight on the last data point than on previous data points. However, any system for calculating weights must be practical to implement. One . way of doing this is the use of a Geometric (or Experiential) - Moving Average. A G'MA_(sometimes called a EWMA) has a parameter, r, which is the weight given to the last data 7 point. The value ofr must be between 0 and 1. _If r: 1, then the. GMA is equivalent to a regular Shewhart Chart on Individuals. Smaller values of r give more smoothing tothe data. Values of r less than 0.5 give rise to problems when starting a GMA since they give too much weight to the initial values. For most applications, r = 0.5 is a suitable value, and makes calculations relatively easy. G1 =X1, _ Gi=rXr+ (1 +r)r X14 +7... +(1 4r)i“_'rX1 i.>_2 -A recursive formula is also available: ' G1 = X1 Gg=rXi+(1—r)Gi_.1 122 * IEIII ‘_ .1 ~ EEIII 'u “ EEIII =~ BEIII :2E ‘0 1,, '0: mmmmmflmmmm .°‘ m mm ammummmmm I!!! 4.0%? .d. .w m N. sagalll aEHEIII aaaalll ,, :IEEIII alumnmmunmmnnm mnnmnmmnmnwmnmmnmm Halli WHERE"!!! |!!!!!!!!l!!|!!|!!!!!!!l!!flfl!!!!!l!!l!!!l!l!! :9 EIII ’ifllflflflfllflflfllflflfl! mnnmmfluuzmmmnmmnmummu Bj gamma]!!! MWHEMMEMMWWMH B BIII . Wfifiifilflmmflfl! |!!!!!!!!ll!!!!!!!!!!l!llfi!!lflfl!l!!!lll!!fl!ll!fl!! EIII HEREIN”!!! mmummnmm 8 _|. F0 0 0 Z _{ 3 O r O I > ID .4 '11 O 33 Control Chart for 6 Mid} {RAM/LE GMA 8: MR CHARTS - Calculation Worksheet MR =I Current Measurement — Previous Measurement l GMA =(r)(Current Measurement )+(1 —r) (Last Average ) flaw: 0.79 = 0308 Total number MES 25' 0 Y =__IalaLoLMeasuLemenis_-__, = 8.79 = Total number of Measurements 25 a 35 3.267 X u 3267 X00308 (2/007 2.12'X‘.oz7 = - 0.35 +0.05? =6.‘1’0? 1.84 X.oz7 = 0-050 1.76 X,oz7 20.098 1.74 x .027 = 0.047 1.73 X .027 =a.o%7 0.35 + 0.050 = 0.?00 0.3.5 +0.0‘I‘8 =0.378 0.35 + 0.0%? = 0.377 0.35 +00%? = o. 3967 0.55 4.0%? = 0.3033 0.35 -— 0.098 = 0.302 0.35 -0.0‘f7 = 0. 505 ...
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Geometric Moving Average Charts - “WEIGHTED MOVING...

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