Monitoring the coefficient of variation using a variable sample size control chart

  • Philippe Castagliola
  • Ali Achouri
  • Hassen Taleb
  • Giovanni Celano
  • Stelios Psarakis


This paper proposes an adaptive Shewhart control chart implementing a variable sample size strategy in order to monitor the coefficient of variation. The goals of this paper are as follows: (a) to propose an easy-to-use 3-parameter logarithmic transformation for the coefficient of variation in order to handle the variable sample size aspect; (b) to derive the formulas for computing the average run length, the standard deviation run length, and the average sample size and to evaluate the performance of the proposed chart based on these criteria; (c) to present ready-to-use tables with optimal chart parameters minimizing the out-of-control average run length as well as the out-of-control average sample size; and (d) to compare this chart with the fixed sampling rate, variable sampling interval, and synthetic control charts. An example illustrates the use of the variable sample size control chart on real data gathered from a casting process.


Coefficient of variation Variable sample size Lognormal transformation Average run length Average sample size Casting process 


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Copyright information

© Springer-Verlag London 2015

Authors and Affiliations

  • Philippe Castagliola
    • 1
  • Ali Achouri
    • 2
  • Hassen Taleb
    • 3
  • Giovanni Celano
    • 4
  • Stelios Psarakis
    • 5
  1. 1.IRCCyN UMR CNRS 6597LUNAM Université, Université de NantesNantesFrance
  2. 2.Institut Suprieur de GestionUniversit de TunisTunisTunisia
  3. 3.Higher Institute of Business Administration of GafsaUniversity of GafsaGafsaTunisia
  4. 4.Department of Industrial EngineeringUniversity of CataniaCataniaItaly
  5. 5.Athens University of Economics and BusinessAthensGreece

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