A Non-parametric Control Chart for Controlling Variability Based on Squared Rank Test

Document Type : Research Paper


SQC-OR Unit, Indian Statistical Institute, 203 B T Road, Kolkata-700108, India


Control charts are used to identify the presence of assignable cause of variation in the process. Non-parametric control chart is an emerging area of recent development in the theory of SPC. Its main advantage is that it does not require any knowledge about the underlying distribution of the variable. In this paper a non-parametric control chart for controlling variability has been developed. Its in control state performances have been computed for different distributions and compared with existing Shewhart S chart. Its efficiency to detect shift in variability has been evaluated.


Main Subjects

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Volume 2, Issue 2 - Serial Number 2
August 2008
Pages 114-125
  • Receive Date: 17 June 2007
  • Revise Date: 23 August 2007
  • Accept Date: 27 August 2008
  • First Publish Date: 27 August 2008