Statistical Papers (09325026)39(4)pp. 347-360
Let X be a random variable and X(w) be a weighted random variable corresponding to X. In this paper, we intend to characterize the Pearson system of distributions by a relationship between reliability measures of X and X(w), for some weight function w>0.
Journal of Multivariate Analysis (0047259X)67(2)pp. 190-202
Recently attempts have been made to characterize probability distributions via truncated expectations in both univariate and multivariate cases. In this paper we will use a well known theorem of Lau and Rao (1982) to obtain some characterization results, based on the truncated expectations of a functionh, for the bivariate Gumbel distribution, a bivariate Lomax distribution, and a bivariate power distribution. The results of the paper subsume some earlier results appearing in the literature. © 1998 Academic Press.
Journal of Statistical Planning and Inference (03783758)81(2)pp. 201-207
Many characterization results of the bivariate exponential distribution and the bivariate geometric distribution have been proved in the literature. Recently Nair and Nair (1988b, Ann. Inst. Statist. Math. 40 (2), 267-271) obtained a characterization result of the Gumbel bivariate exponential distribution and a bivariate geometric distribution based on truncated moments. In this note, we extend the results of to obtain a general result, characterizing these two bivariate distributions based on the truncated expectation of a function h, satisfying some mild conditions.
Metrika (1435926X)49(2)pp. 121-126
In this paper, we characterize some multivariate distributions based on a relationship between the multivariate hazard rate, as defined by Johnson and Kotz (1975) and Marshall (1975), and the multivariate mean residual life as defined by Arnold and Zahedi (1988). The results are extensions of the results obtained earlier by Roy (1989, 1990) and Ma (1996, 1997).
Statistics and Probability Letters (01677152)49(3)pp. 263-269
A direct approach to measure uncertainty in the residual life time distribution has been initiated by Ebrahimi (1996, Sankhya Ser. A 58, 48-57) and explored further by Ebrahimi and Pellerey (1995) and Ebrahimi and Kirmani (1996). In this paper, some new properties of the proposed measure in connection to order statistics and record values are derived. The generalized Pareto distribution has been widely used in the literature. We have also given several characterizations of this distribution in terms of the proposed measure.
Handbook of Statistics (01697161)20pp. 199-214
Asadi, M.,
Ebrahimi, N.,
Hamedani, G.,
Soofi, E.S. Journal of Applied Probability (00219002)41(2)pp. 379-390
A formal approach to produce a model for the data-generating distribution based on partial knowledge is the well-known maximum entropy method. In this approach, partial knowledge about the data-generating distribution is formulated in terms of some information constraints and the model is obtained by maximizing the Shannon entropy under these constraints. Frequently, in reliability analysis the problem of interest is the lifetime beyond an age t. In such cases, the distribution of interest for computing uncertainty and information is the residual distribution. The information functions involving a residual life distribution depend on t, and hence are dynamic. The maximum dynamic entropy (MDE) model is the distribution with the density that maximizes the dynamic entropy for all t. We provide a result that relates the orderings of dynamic entropy and the hazard function for distributions with monotone densities. Applications include dynamic entropy ordering within some parametric families of distributions, orderings of distributions of lifetimes of systems and their components connected in series and parallel, record values, and formulation of constraints for the MDE model in terms of the evolution paths of the hazard function and mean residual lifetime function. In particular, we identify classes of distributions in which some well-known distributions, including the mixture of two exponential distributions and the mixture of two Pareto distributions, are the MDE models.
Communications in Statistics - Theory and Methods (1532415X)34(2)pp. 475-484
One of the most important types of system structures is the parallel structure. In the present article, we propose a definition for the mean residual life function of a parallel system and obtain some of its properties. The proposed definition measures the mean residual life function of a parallel system consisting of n identical and independent components wider the condition that n -i, i = 0, 2,..., n -1, components of the system are working and other components of the system have already failed. It is shown that, for the case where the components of the system have increasing hazard rate, the mean residual life function of the system is a nonincreasing function of time. Finally, we will obtain an upper bound for the proposed mean residual life function. Copyright © Taylor & Francis, Inc.
Stochastic Processes and their Applications (3044149)115(11)pp. 1838-1859
The spectral structure of discrete time periodically correlated (as well as multivariate stationary) symmetric α-stable processes is identified by decomposing such a process uniquely in distribution into one sum of three mutually independent periodically correlated (multivariate stationary) stable processes that are classified as mixed moving average, harmonizable and of a third kind. The techniques are based on presenting the flow and its cocycle that govern the spectral representation of the process, using the Hopf decomposition and specifying the harmonizable component. © 2005 Elsevier B.V. All rights reserved.
Journal of Statistical Planning and Inference (03783758)136(4)pp. 1197-1206
In the study of reliability of the technical systems and subsystems, parallel systems play a very important role. In the present paper, we consider a parallel system consisting of n identical components with independent lifetimes having a common distribution function F. It is assumed that at time t the system has failed. Under these conditions, we obtain the mean past lifetime (MPL) of the components of the system. Some properties of MPL are studied. It is shown that the underlying distribution function F can be recovered from the proposed MPL. Also, a comparison between two parallel systems are made based on their MPLs in the case where the components of the system are ordered in terms of reversed hazard rate. Finally a characterization of the uniform distribution is given based on MPL. © 2004 Elsevier B.V. All rights reserved.
Theory of Probability and its Applications (0040585X)50(3)pp. 448-462
A simple random measure is a finite sum of random measures with disjoint supports. A type of simple random measure which is induced by a multivariate random measure (Φ1, . . . , Φm) and measurable mappings T1, . . . , Tm is introduced and studied. Interestingly it gives rise to introducing a class of processes, called simple, that include stationary processes and discrete time periodically correlated processes. This study involves spectral domain and time domain characterizations and simulation. The role of spectral kernels in analysis of nonstationary processes is also discussed. © 2006 Society for Industrial and Applied Mathematics.
IEEE Transactions on Reliability (15581721)55(2)pp. 314-318
In the study of the reliability of technical systems, k-out-of-n systems play an important role. In the present paper, we consider k-out-of-n system consisting of n identical components with independent lifetimes having a common distribution function F. Under the condition that, at time t, all the components of the system are working, we propose a new definition for the mean residual life (MRL) function of the system, and obtain several properties of that system. © 2006 IEEE.
Communications in Statistics - Theory and Methods (1532415X)36(7)pp. 1333-1341
In recent years, several attempts have been made to characterize the generalized Pareto distributions (GPD) based on the properties of order statistics and record values. In the present article, we give some characterization results on GPD based on order statistics and generalized order statistics. Some characterizations of uniform distribution based on expectation of some functions of order statistics are also given.
Journal of Statistical Planning and Inference (03783758)137(6)pp. 1931-1941
Recently, Rao et al. [(2004) Cumulative residual entropy: a new measure of information. IEEE Trans. Inform. Theory 50(6), 1220-1228] have proposed a new measure of uncertainty, called cumulative residual entropy (CRE), in a distribution function F and obtained some properties and applications of that. In the present paper, we propose a dynamic form of CRE and obtain some of its properties. We show how CRE (and its dynamic version) is connected with well-known reliability measures such as the mean residual life time. © 2006 Elsevier B.V. All rights reserved.
Balali, G.,
Hadi m.r., ,
Yavari p., ,
Bidram, H.,
Naderi a.g., ,
Eslami a., African Journal of Biotechnology (16845315)7(9)pp. 1265-1270
This study was carried out to evaluate the effects of pot size, planting date and type of genotype on mini-tuber production of Marfona potato cultivar (Solanum tuberosum L.) in greenhouse conditions. Four genotypes (M-129, M-128P, M-127P and M-124P) originated from virus free sprouts and a genotype of the same cultivar (Marfona) originated from apical meristem, in 3 sizes of pot and 3 planting date were investigated. The results showed that using larger pots of 3-liter has no advantage and pots smaller than 2-liter is not suitable for mini-tuber production. Also, time of Nov 18 was the best of date for planting of potato in studied conditions and delay in date of planting reduced the mini-tuber production. The reduction in number of mini-tubers and growing period was greater for the genotype M-129 compared with the other potato genotypes. Furthermore, higher numbers of mini-tubers were produced by the M-127P and M-124P genotypes and M-127P had the highest total weight of mini-tubers. However the number of mini-tubers per plant was higher for genotypes originated from meristem culture than genotypes obtained from sprouts. It seems that genotypes originated from potato sprouts are not as efficient as the apical meristem ones. On the other hand, later genotype showed more homogenous in growth rate and phenotype. © 2008 Academic Journals.
Communications in Statistics - Theory and Methods (1532415X)37(9)pp. 1347-1352
In recent years, several attempts have been made to characterize the generalized Pareto distribution (GPD) based on the properties of order statistics and record values. In the present article, we give a characterization result on GPD based on the spacing of generalized order statistics.
Metrika (1435926X)68(2)pp. 209-217
Let T denote a positive discrete survival time and n a non-negative integer number. Properties of the mean past lifetime E(n - T|T < n) are provided. © 2007 Springer-Verlag.
IEEE Transactions on Reliability (15581721)57(4)pp. 574-580
We consider a coherent structure consisting of n components having the property that if it is known that at most r components (r[removed]
Journal of Statistical Planning and Inference (03783758)138(12)pp. 3660-3666
Suppose that a technical system is subject to shocks, e.g. peaks of voltages from a sequence of identically independent voltages having a lower limit value v > 0. We propose a new definition for the mean residual life of the records of the sequence and study its various properties. © 2008 Elsevier B.V. All rights reserved.
ANZIAM Journal (14461811)51(SUPPL.)
We consider systems having many independent components connected in a parallel or series configuration with non-identical failure distributions. A time dependent measure is proposed which evaluate the probability that a failure of the system occurred at a specified component under the condition that the system has failed by some time. We proved several properties of this measure for parallel and serial systems. © Austral. Mathematical Soc. 2010.
Computers and Geosciences (00983004)35(3)pp. 626-634
In this paper, the finite strain data (FSD) collected from a Sheeprock thrust sheet in Utah are spatially analyzed. The steps and special manner of spatial analysis of these data are examined due to the importance and influence of data characteristics on spatial prediction accuracy. To do so, the exponential and spherical parametric variogram models with and without nugget effects are fitted by maximum likelihood and restricted maximum likelihood methods on original and normally transformed data. We also fitted other models to classical and robust empirical variograms by ordinary least squares and weighted least squares methods. Next, these models are applied on data and edited data by using robust kriging. Finally, the accuracy of the obtained results are compared with Mukul's model by cross-validation in order to choose the best variogram model for FSD and also specify the importance of attention to characteristics of the data in spatial data analysis. © 2008 Elsevier Ltd. All rights reserved.
European Journal of Social Sciences (discontinued) (14502267)15(4)pp. 599-610
Management is increasingly transforming to Knowledge management. This means that we manage Knowledge of people not themselves, and leadership means providing good condition for producing valued Knowledge by human and accomplishing this by the way that persuade people to accountability. Contemporary clear sighted says that Knowledge is considered as the main source of competitive advantage, and for the organizations to achieve such advantage. This paper seeks for Amount of Paying Attention to Knowledge Management in Automobile Industry of Iran. The results indicate that there has been attention to creating, maintaining, and disseminating and applying knowledge management in Automobile Industry Findings of data analysis show that in Iran's automobile industry, attention paid to creating, maintaining, sharing, applying and generally knowledge management has been lower than the intended amount.
Metrika (1435926X)72(1)pp. 59-73
In the present paper, we consider a (n - k + 1)-out-of-n system with identical components where it is assumed that the lifetimes of the components are independent and have a common distribution function F. We assume that the system fails at time t or sometime before t, t > 0. Under these conditions, we are interested in the study of the mean time elapsed since the failure of the components. We call this as the mean past lifetime (MPL) of the components at the system level. Several properties of the MPL are studied. It is proved that the relation between the proposed MPL and the underlying distribution is one-to-one. We have shown that when the components of the system have decreasing reversed hazard then the MPL of the system is increasing with respect to time. Some examples are also provided. © Springer-Verlag 2009.
Asl, N.S.,
Dost, H.N.,
Kalantery, M.,
Talebi, H.,
Khosravi, A. Koomesh (23453699)11(4)pp. 294-302
Introduction: Essential hypertension is one of the most important factors on quality of life and third casual of death in the world. The purpose of the present study was to determine the effect of cognitive behavioral therapy and drug therapy on improvement of quality of life in the patients with essential hypertension. Materials and Methods: This clinical trial was performed in Heart center of Medical Uuniversity of Isfahan (Iran) between April 2007 and April 2008. 40 Patients with essential hypertension were selected randomly and assigned into 2 groups: experimental group that received cognitive behavioral therapy and control group with drug therapy. All of the patients completed the quality of life and a demographic questionnaire before start of interventions as pre test. The post test was completed after the end of intervention and follow up completed after 4 month later. Results: Findings showed that cognitive behavioral therapy was more effective than drug therapy on improvement of quality of life in the patients with essential hypertension in post test and follow up. Conclusion: Cognitive behavioral therapy was effective on improvement of quality of life in the patients with essential hypertension. According to findings of this work, we suggest that team work approach consist of psychologists and heart professional can be useful for treatment of quality of life in the patients with essential hypertension.
Statistica Neerlandica (00390402)64(4)pp. 460-481
Let the random variables X and Y denote the lifetimes of two systems. In reliability theory to compare between the lifetimes of X and Y there are several approaches. Among the most popular methods of comparing the lifetimes are to compare the survival functions, the failure rates and the mean residual lifetime functions of X and Y. Assume that both systems are operating at time t > 0. Then the residual lifetimes of them are Xt=X-t | X>t and Yt=Y-t | Y>t, respectively. In this paper, we introduce, by taking into account the age of systems, a time-dependent criterion to compare the residual lifetimes of them. In other words, we concentrate on function R(t):=P(Xt>Yt) which enables one to obtain, at time t, the probability that the residual lifetime Xt is greater than the residual lifetime Yt. It is mentioned, in Brown and Rutemiller (IEEE Transactions on Reliability, 22, 1973) that the probability of type R(t) is important for designing as long-lived a product as possible. Several properties of R(t) and its connection with well-known reliability measures are investigated. The estimation of R(t) based on samples from X and Y is also discussed. © 2010 The Authors. Statistica Neerlandica © 2010 VVS.
Probability in the Engineering and Informational Sciences (02699648)24(4)pp. 561-584
This article develops information optimal models for the joint distribution based on partial information about the survival function or hazard gradient in terms of inequalities. In the class of all distributions that satisfy the partial information, the optimal model is characterized by well-known information criteria. General results relate these information criteria with the upper orthant and the hazard gradient orderings. Applications include information characterizations of the bivariate Farlie-Gumbel-Morgenstern, bivariate Gumbel, and bivariate generalized Gumbel, for which no other information characterization are available. The generalized bivariate Gumbel model is obtained from partial information about the survival function and hazard gradient in terms of marginal hazard rates. Other examples include dynamic information characterizations of the bivariate Lomax and generalized bivariate Gumbel models having marginals that are transformations of exponential such as Pareto, Weibull, and extreme value. Mixtures of bivariate Gumbel and generalized Gumbel are obtained from partial information given in terms of mixtures of the marginal hazard rates. Copyright © 2010 Cambridge University Press.
Applied Mathematical Sciences (discontinued) (1312885X)4(61-64)pp. 3067-3082
In this paper some models are applied to analyze insomnia data. Insomnia is a sleep disorder in which the patient does not get enough or satisfactory sleep and investigating the use of hypnotic drug for its cure is so important. For studying the effect of drugs on insomnia, it is useful to observe the response of interest (cured or not cured) for each subject repeatedly at several times. So, a longitudinal study of repeated binary responses along with a treatment variable (with two levels hypnotic or placebo) are used for some individuals on two times. A very important feature of the data is that the correlation between the two longitudinal responses depends on the level of hypnotic drug. This is, firstly, shown by an exploratory data analysis. Then, as an option, Dale's bivariate model for analyzing longitudinal or repeated measurements of binary responses, considering the effect of treatment on the responses and the correlation structure, is used to find an overall population effect on the responses. As other options, transition and random effect models for analyzing these data are used to investigate, respectively, the reasons for the change of the responses and to find the subject-specific variations. How the interpretation of the results is different with the use of the Dale's model and how one may find out the effect of the drug on the correlation structure by a transition or random effect model are also discussed.
Information Sciences (00200255)180(21)pp. 4195-4206
This paper explores properties of the residual Rényi entropy of some ordered random variables. The residual Rényi entropy of the kth order statistic from a continuous distribution function is represented in terms of the residual Rényi entropy of the kth order statistic from uniform distribution. The monotone behavior of the residual Rényi entropy of order statistic under various conditions is discussed. Analogues results for the residual Rényi entropy of record values are also given. © 2010 Published by Elsevier Inc.
