Quality Management 2017

A NALYZE

14. Control charts building: calculation of control limits

• Control limits (= natural limits of the process = “voice of the process”) :  Process’s production is not always identical  Mean

Part 1 :

Introduction to SPC

Mean - 3 

Mean + 3 

 Normal distribution (central limit theorem )

LCL

UCL

Control lim

Control lim

Part 2 :

Natural dispersion

0.135%

0.135%

Essential concepts to start with SPC

 To be checked.

=  risk

=  risk

> 99%

A point falls outside the natural limits special cause with certain  risk (0.27%) common causes

Part 3 :

• Analysis of control charts Carte de contrôle des valeurs individuelles

SPC in practice

3,0%

3 potential special causes

2,5%

UCL

2,0%

1,5%

Part 4

1,0%

Mean

Details of limits’ calculation

X

0,5%

Conclusion

0,0%

6 points

-0,5%

LCL

Individual Value (%)

• Book of M. Pillet, Appliquer la Maitrise Statistique des Processus (2005)

-1,0%

9 points

-1,5%

0 10 Monitored parameter

20

30

40

• Thesis K. Gérard (2008)

Patient number Data (chronological order)

• ESTRO Practical exercise, Torino (2015) • T. Pawlicki, SPC for radiotherapy QA (2005)

03/10/17