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Optimal Design of ALT under Progressive Type I Interval Censoring with Random Removals. Tse, Siu-Keung Department of Management Sciences, City University of Hong Kong, HK Yang, Chunyan (speaker) Department of Statistics, Yunnan University, PRC Ding, Chang
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Optimal Design of ALT under Progressive Type I Interval Censoring with Random Removals Tse, Siu-Keung Department of Management Sciences, City University of Hong Kong, HK Yang, Chunyan (speaker) Department of Statistics, Yunnan University, PRC Ding, Chang Department of Statistics, Yunnan University, PRC
Quality Reliability normal complete Life tests censoring accelerated continuous periodic various types of accelerated life tests (ALT)
ni1 ni2 niki 0 ti1 ti2 tiki ALT under Type I censoring with periodic inspection: Yum & Choi (1989) i=1: low stress level (s1) i=2: high stress level (s2)
ri1 ri2 riki ni1 ni2 niki 0 ti1 ti2 tiki Removal: budget, inspection, test specimen fixed or random? Yuen & Tse (1996) ALT under progressive Type I interval censoring with random removals
ri1 ri2 riki (allocation proportion) 3. lifetime 1. constant 2. Xi1 Xi2 Xiki 0 ti1 ti2 tiki Assumptions:
4. observed data, binomial distribution. such that the qth quantile is estimated accurately (that is, AV( ) minimized). • Optimal design: • Inspection time: {tij, i=1,2,…, m; j=1, 2,…, ki} • The stress level: si, i=1,2,…, m-1. • Allocation of test units: ai , ni= ain
such that the corresponding is minimized. 3.1 Statistically Optimal (SO) Plans (m=2)
3.2 Equally Spaced (ES) Plan (m=2) The inspection is conducted at the time points with equal space. pre-specified 3.3 Equal Probability (EP) Plan (m=2) The inspection times are selected such that the probability of failure in each interval is the same.
pre-specified 3.4 ES and EP Plans (m=3) provide a mean to check the straight-line relationship assumed
Conclusions: • a. SO plans always produce the smallest AV and stable over k and p. b. the performance of ES and EP are similar to those of SO plans, especially when p = 0. c. EP plans are relatively better than ES plans, especially when p> 0.