Journal of the Iranian Statistical Society
http://jirss@irstat.ir
Journal of The Iranian Statistical Society - Journal articles for year 2016, Volume 15, Number 1Yektaweb Collection - http://www.yektaweb.comen2016/7/11Estimation of the Conditional Survival Function of a Failure Time Given a Time-varying Covariate with Interval-censored Observations
http://jirss.irstat.ir/browse.php?a_id=374&sid=1&slc_lang=en
<p>In this paper, we propose an approach for the nonparametric estimation of the conditional survival function of a time to failure‎ ‎given a time-varying covariate under interval-censoring for the failure time. Our strategy consists in‎ ‎modeling the covariate path with a random effects model, ‎as is done in the degradation and joint longitudinal and survival data modeling‎ ‎literature, ‎then in using a nonparametric estimator of the conditional survival function for time-fixed covariate. ‎We derive the large sample bias and variance of the estimator under simplifying assumptions and we investigate‎ ‎its finite sample efficiency and robustness by simulation. ‎We show how the proposed method can be useful in‎ ‎the early stages of data exploration and model specification by applying it to two real datasets, ‎one on‎ ‎the time to infestation of trees by pine weevil and one on the reliability of a piece of electrical equipment. ‎We conclude by suggesting avenues to make this data exploration method more suitable for formal inferences‎.</p>
Mohammad Hossein DehghanOn Gamma Regression Residuals
http://jirss.irstat.ir/browse.php?a_id=368&sid=1&slc_lang=en
<p style="margin-top: 0px; margin-bottom: 0px;">In this paper, ‎we propose new residuals for gamma regression models, ‎assuming that both mean and shape parameters follow regression structures. The models are summarized and fitted by applying both classic and Bayesian methods as proposed by Cepeda-Cuervo (2001). The residuals are proposed from properties of the biparametric exponential family of distributions. ‎Simulated and real data sets‎ ‎are analyzed to determine the performance and behavior of the proposed residuals. ‎</p>
Edilberto Cepeda-CuervoStochastic Comparisons of Series and Parallel Systems with Heterogeneous Extended Generalized Exponential Components
http://jirss.irstat.ir/browse.php?a_id=364&sid=1&slc_lang=en
<p style="margin-top: 0px; margin-bottom: 0px;">In this paper, we discuss the usual stochastic‎, ‎likelihood ratio, ‎dispersive and convex transform order between two parallel systems with independent heterogeneous extended generalized exponential components. ‎We also establish the usual stochastic order between series systems from two independent heterogeneous extended generalized exponential samples. ‎Finally, ‎we find lower and upper bounds for the Renyi entropy and cumulative residual entropy of series and parallel systems‎.</p>
Amir T. Payandeh NajafabadiDistribution of Order Statistics for Exchangeable Random Variables
http://jirss.irstat.ir/browse.php?a_id=365&sid=1&slc_lang=en
<p>Let T<sub>1</sub>,...,T<sub>n</sub> be exchangeable random variables and suppose that T<sub>{1:n} </sub>represents the ith order statistic among T<sub>i</sub>'s, i=1,...,n. ‎In this paper some expressions for the joint distribution ‎of (T<sub>{1:n}</sub>,...,T<sub>{n:n}</sub>), ‎marginal distribution of T<sub>{1:n} </sub>and the joint distribution of (T<sub>{r:n}</sub>,T<sub>{k:n}</sub>), 1≤ r ≤ k ≤n ‎in terms of the joint distribution (or joint reliability) function of T<sub>i</sub>'s are provided. ‎Using these and when {T<sub>1,...,</sub>T<sub>n</sub>} is a sequence of‎ ‎lifetimes, some expressions for the mean residual life functions of a n-k+1-out-of-n system‎, H<sub>n</sub><sup>k(</sup>t)=E(T<sub>{k:n}</sub>-t|T<sub>{1:n}</sub>>t) and M<sub>n</sub><sup>{r,k}</sup>(t)=E(T<sub>{k:n}</sub>-t|T<sub>{r:n}</sub>>t), ‎1≤ r≤ k≤ n in terms of the joint survival function of T<sub>i</sub>'s are given‎. ‎Also, ‎some examples are provided‎. </p>
Mohammad Khanjari SadeghA Kotz-Riesz-Type Distribution
http://jirss.irstat.ir/browse.php?a_id=330&sid=1&slc_lang=en
<p>This article derives the distribution of random matrix X associated with the transformation Y = X*X, such that Y has a Riesz distribution for real normed division algebras. Two versions of this distributions are proposed and some of their properties are studied.</p>
Jose A. Diaz-GarciaThe Beta-Weibull Logaritmic Distribution: Some Properties and Applications
http://jirss.irstat.ir/browse.php?a_id=287&sid=1&slc_lang=en
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<span style="font-family:times new roman;"><span style=" color:#000000;">In this paper, we introduce a new five-parameter distribution with increasing, decreasing, bathtub-shaped failure rate called the Beta-Weibull-Logarithmic (BWL) distribution. Using the Sterling Polynomials, various properties of the new distribution such as its probability density function, its reliability and failure rate functions, quantiles and moments, R</span><span style=" color:#008000;">$acute{e}$</span><span style=" color:#000000;">nyi and Shannon entropies, moments of order statistics, Bonferroni and Lorenz curves were derived. then the maximum likelihood estimation of BWL distribution for the parameters of BWL distribution are found. Finally the usefulness of this distribution for real data are presented. </span></span></pre>
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Shahram Yaghoobzadeh Shahrastani