Sains Malaysiana 30: 87-106 (2001)                                                                                                    Pengajian Kuantitatif/

Quantitative Studies


A Modified Nonparametric Univariate Control Chart for

Location Based on the Trimmed Mean



Moustafa O, Abu-Shawiesh

Department of Staistics

College of Management Sciences and Planning

King Faisal University, P.O. Box 1760

Al-Ahsa 31982, Kingdom of Arab Saudi


Mokhtar B. Abdullah

School of Mathematical Sciences

Faculty Science and Technology

Universiti Kebangsaan Malaysia

43600 UKM Bangi

Selangor D.E. Malaysia






Rencana ini mengemukakan ubahsuaian kepada had kawalan dan garis tengah Carta Kawalan Hodges-Lehmann yang dicadangkan oleh Alloway dan Raghavachari (1991).  Ubahsuaian ini dilakukan dengan menggantikan median purata Walsh dengan min terpangkas-a dalam penganggar Hodges-Lehmann.  Contoh berangka ditunjukkan bagi menerangkan kaedah baru ini. Prestasinya dibandingkan dengan prestasi kaedah Alloway & Raghavachari (1991) menerusi kajian simulasi.





This paper develops a modified approach to the computation of control limits and central line for the Hodges-Lehmann control chart proposed by Alloway & Raghavachari (1991).  The modified approach is based on replacing the median of the Walsh averages by the a-trimmed mean, in the Hodges-Lehmann estimator. A numerical example is given to illustrate the use of the modified approach. It is performance is compared with that of Alloway & Raghavachari (1991) using some simulation studies.





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