Department of Basic Sciences, College of Science and Theoretical Studies, Saudi Electronic University, Dammam 32256, Saudi Arabia.
Department of Mathematics and Sciences, College of Arts & Applied Sciences, Dhofar University, Salalah, Oman.
Comput Intell Neurosci. 2022 Apr 28;2022:3491732. doi: 10.1155/2022/3491732. eCollection 2022.
A long testing period is usually required for the life testing of high-reliability products or materials. It is possible to shorten the testing process by using ALTs (accelerated life tests). Due to the fact that ALTs test products in harsher settings than are typical use conditions, the life expectancy of the objects they evaluate is reduced. Censored data in which the specific failure timings of all units assigned to test are not known, or all units assigned to test have not failed, may arise in ALTs for a variety of reasons, including operational failure, device malfunction, expense, and time restrictions. In this paper, we have considered the step stress partially accelerated life test (SSPALT) under two different censoring schemes, namely the type-I progressive hybrid censoring scheme (type-I PHCS) and the type-II progressive censorship scheme (type-II PCS). The failure times of the items are assumed to follow NH distribution, while the tampered random variable (TRV) model is used to explain the effect of stress change. In order to obtain the estimates of the unknown parameters, the maximum likelihood estimation (MLE) approach is adopted. Furthermore, based on the asymptotic theory of MLEs, the approximate confidence intervals (ACIs) are also constructed. The point estimates under two censoring schemes are compared in terms of root mean squared errors (RMSEs) and relative absolute biases (RABs), while ACIs are compared in terms of their lengths and coverage probabilities (CPs). The performance of the estimators has been evaluated and compared under two censoring schemes with various sample sizes through a simulation study. Simulation results show that estimates with type-I PHCS outperform estimates with type-II PCS in terms of RMSEs, RABs, lengths, and CPs. Finally, a real-world numerical example of insulating fluid failure times is presented to show how the approaches will work in reality.
高可靠性产品或材料的寿命测试通常需要较长的测试周期。通过使用 ALT（加速寿命测试）可以缩短测试过程。由于 ALT 在比典型使用条件更苛刻的环境下测试产品，因此它们评估的对象的预期寿命会缩短。由于各种原因，包括操作故障、设备故障、费用和时间限制，ALT 中可能会出现截尾数据，即在测试中分配的所有单位的具体失效时间未知，或者所有分配给测试的单位都没有失效。在本文中，我们考虑了两种不同的截尾方案下的阶跃应力部分加速寿命测试（SSPALT），即 I 型逐次混合截尾方案（I 型 PHCS）和 II 型逐次截尾方案（II 型 PCS）。假设项目的失效时间服从 NH 分布，而篡改随机变量（TRV）模型用于解释应力变化的影响。为了获得未知参数的估计值，采用了最大似然估计（MLE）方法。此外，基于 MLE 的渐近理论，还构建了近似置信区间（ACI）。在两种截尾方案下，根据均方根误差（RMSE）和相对绝对偏差（RAB）比较点估计，根据长度和覆盖概率（CP）比较 ACI。通过模拟研究，在两种截尾方案下，针对不同样本量评估和比较了估计量的性能。模拟结果表明，在 RMSE、RAB、长度和 CP 方面，I 型 PHCS 的估计值优于 II 型 PCS 的估计值。最后，提出了一个绝缘液失效时间的实际数值示例，以展示这些方法在实际中的应用。
