Optimal average sample number of the SPRT chart for monitoring fraction nonconforming

Salah Haridy, Zhang Wu, Ka Man Lee, Nadia Bhuiyan

Research output: Journal article publicationJournal articleAcademic researchpeer-review

22 Citations (Scopus)


The Sequential Probability Ratio Test (SPRT) control chart is a powerful tool for monitoring manufacturing processes. It is highly suitable for the applications where testing is destructive or very expensive, such as the automobile airbags test. This article studies the effect of the Average Sample Number (ASN) (i.e., the average sample size) on the chart's performance. A design algorithm is proposed to develop the optimal SPRT chart for monitoring the fraction nonconforming p of Bernoulli processes. By optimizing the ASN and other charting parameters, the average detection speed of the SPRT chart is almost doubled. It is also found that the optimal SPRT chart significantly outperforms the optimal np and binomial CUSUM charts, in terms of Average Number of Defectives (AND), under different combinations of the design specifications. It is observed that the SPRT chart using a relatively smaller ASN and a shorter sampling interval (h) has a higher overall detection effectiveness.
Original languageEnglish
Pages (from-to)411-421
Number of pages11
JournalEuropean Journal of Operational Research
Issue number2
Publication statusPublished - 1 Sept 2013


  • Sequential Probability Ratio Test (SPRT) Control chart Average Sample Number (ASN) Average Number of Defectives (AND) Sampling interval

ASJC Scopus subject areas

  • Modelling and Simulation
  • Management Science and Operations Research
  • Information Systems and Management


Dive into the research topics of 'Optimal average sample number of the SPRT chart for monitoring fraction nonconforming'. Together they form a unique fingerprint.

Cite this