Quality Management 2017

A NALYZE

13. Control charts building: EWMA

Type of drifts to detect

Control charts

Part 1 :

Introduction to SPC

Ex.: wrong adjustment of linac’s parameters, errors during measurement…

Large and Fast

Individual value / Moving Range Individual va o i nge

(I,MR)

Part 2 :

Patient number

Diff. mes/calc. (%)

Essential concepts to start with SPC

EWMA - Exponentially Weighted Moving Average -

Ex.: drift of the detector’s dose response

Small and slow

Part 3 :

Patient number Diff. mes/calc. (%)

SPC in practice

Building EWMA control chart

coefficient

coefficient

Ex:  = 0.2  Importance of 20% for x i (current value)  Importance of 80% for M i-1 (previous values)

M

  

M) 1( x

i

i



1i

Part 4

Conclusion

Current value Previous values

M

value current

values previsous



 2.0



 8.0

03/10/17

i

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0