• 제목/요약/키워드: ARL-unbiased

검색결과 2건 처리시간 0.029초

Optimal Designs for Attribute Control Charts

  • Chung, Sung-Hee;Park, Sung-Hyun;Park, Jun-Oh
    • 한국통계학회:학술대회논문집
    • /
    • 한국통계학회 2003년도 추계 학술발표회 논문집
    • /
    • pp.97-103
    • /
    • 2003
  • Shewhart-type control charts have historically been used for attribute data, though they have ARL biased property and even are unable to detect the improvement of a process with some process parameters. So far most efforts have been made to improve the performance of attribute control charts in terms of faster detection of special causes without increasing the rates of false alarm. In this paper, control limits are proposed that yield an ARL (nearly) unbiased chart for attributes. Optimal design is also proposed for attribute control charts under a natural sense of criterion.

  • PDF

X Control Charts under the Second Order Autoregressive Process

  • Baik, Jai-Wook
    • 품질경영학회지
    • /
    • 제22권1호
    • /
    • pp.82-95
    • /
    • 1994
  • When independent individual measurements are taken both $S/c_4$ and $\bar{R}/d_2$ are unbiased estimators of the process standard deviation. However, with dependent data $\bar{R}/d_2$ is not an unbiased estimator of the process standard deviation. On the other hand $S/c_4$ is an asymptotic unbiased estimator. If there exists correlation in the data, positive(negative) correlation tends to increase(decrease) the ARL. The effect of using $\bar{R}/d_2$ is greater than $S/c_4$ if the assumption of independence is invalid. Supplementary runs rule shortens the ARL of X control charts dramatically in the presence of correlation in the data.

  • PDF