Abstract:Fisher information about multiple parameters in a progressively Type-II censored sample is discussed. A representation of the Fisher information matrix in terms of the hazard rate of the baseline distribution is established which can be used for efficient computation of the Fisher information. This expression generalizes a result of Zheng and Park [On the Fisher information in multiply censored and progressively censored data, Comm. Statist. Theory Methods 33 (2004), pp. 1821-1835 for Fisher information about … Show more
“…The A-optimality criterion uses the sum of variances of the estimated model parameters as utility function ψ, whereas the D-optimality criterion uses an overall measure of variability given by the determinant of the covariance matrix of the estimated model parameters (see Liski et al 2002). Ng et al (2004), Balakrishnan et al (2008) and Dahmen et al (2012) considered A-and D-optimal criteria for Weibull, Lomax, normal and extreme value distributions in the context of Type-II progressive censoring scheme. Instead of using traditional A-and D-optimal criteria, Kundu (2009, 2013) considered an optimality criterion based on estimated pth quantile of the distribution of lifetime T .…”
“…The corresponding Fisher information matrix for vector parameter θ is given by Dahmen et al (2012) gave a direct computation formula for Fisher information matrix as…”
In determination of optimum Type-II progressive censoring scheme, the experimenter needs to carry out an exhaustive search within the set of all admissible censoring schemes. The existing recommendations are only applicable for small sample sizes. The implementation of exhaustive search techniques for large sample sizes is not feasible in practice. In this article, a meta-heuristic algorithm based on variable neighborhood search approach is proposed for large sample sizes. It is found that the algorithm gives exactly the same solution for small sample sizes as the solution obtained in an exhaustive search; however, for large sample sizes, it gives near-optimum solution. We have proposed a cost function-based optimum criterion, which is scale invariant for location-scale and log-location-scale families of distribution. A sensitivity analysis is also considered to study the effect of misspecification of parameter values or cost coefficients on the optimum solution.
“…The A-optimality criterion uses the sum of variances of the estimated model parameters as utility function ψ, whereas the D-optimality criterion uses an overall measure of variability given by the determinant of the covariance matrix of the estimated model parameters (see Liski et al 2002). Ng et al (2004), Balakrishnan et al (2008) and Dahmen et al (2012) considered A-and D-optimal criteria for Weibull, Lomax, normal and extreme value distributions in the context of Type-II progressive censoring scheme. Instead of using traditional A-and D-optimal criteria, Kundu (2009, 2013) considered an optimality criterion based on estimated pth quantile of the distribution of lifetime T .…”
“…The corresponding Fisher information matrix for vector parameter θ is given by Dahmen et al (2012) gave a direct computation formula for Fisher information matrix as…”
In determination of optimum Type-II progressive censoring scheme, the experimenter needs to carry out an exhaustive search within the set of all admissible censoring schemes. The existing recommendations are only applicable for small sample sizes. The implementation of exhaustive search techniques for large sample sizes is not feasible in practice. In this article, a meta-heuristic algorithm based on variable neighborhood search approach is proposed for large sample sizes. It is found that the algorithm gives exactly the same solution for small sample sizes as the solution obtained in an exhaustive search; however, for large sample sizes, it gives near-optimum solution. We have proposed a cost function-based optimum criterion, which is scale invariant for location-scale and log-location-scale families of distribution. A sensitivity analysis is also considered to study the effect of misspecification of parameter values or cost coefficients on the optimum solution.
In the design of constant-stress life-testing experiments, the optimal allocation in a multi-level stress test with Type-I or Type-II censoring based on the Weibull regression model has been studied in the literature. Conventional Type-I and Type-II censoring schemes restrict our ability to observe extreme failures in the experiment and these extreme failures are important in the estimation of upper quantiles and understanding of the tail behaviors of the lifetime distribution. For this reason, we propose the use of progressive extremal censoring at each stress level, whereas the conventional Type-II censoring is a special case. The proposed experimental scheme allows some extreme failures to be observed. The maximum likelihood estimators of the model parameters, the Fisher information and asymptotic variance-covariance matrices of the maximum likelihood estimates are derived. We consider the optimal experimental planning problem by looking at four different optimality criteria. To avoid the computational burden in searching for the optimal allocation, a simple search procedure is suggested. Optimal allocation of units for 2-and 4-stress-level situations are determined numerically. The asymptotic Fisher information matrix and the asymptotic optimal allocation problem are also studied and the results are compared with optimal allocations with specified sample sizes. Finally, conclusions and some practical recommendations are provided.
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