Journal of the Iranian Statistical Society
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Journal of The Iranian Statistical Society - Journal articles for year 2013, Volume 12, Number 2Yektaweb Collection - http://www.yektaweb.comen2013/10/9Optimal Simple Step-Stress Plan for Type-I Censored Data from Geometric Distribution
http://jirss.irstat.ir/browse.php?a_id=229&sid=1&slc_lang=en
Abstract. A simple step-stress accelerated life testing plan is considered when the failure times in each level of stress are geometrically distributed under Type-I censoring. The problem of choosing the optimal plan is investigated using the asymptotic variance-optimality as well as determinant-optimality and probability-optimality criteria. To illustrate the results of the paper, an example is presented and a sensitivity analysis is performed. A simulation study is also done to investigate the robustness of the criteria with respect to estimation error of the parameters. Eventually, some conclusions are presented.A. AreOn the Maximum Likelihood Estimators for some Generalized Pareto-like Frequency Distribution
http://jirss.irstat.ir/browse.php?a_id=230&sid=1&slc_lang=en
Abstract. In this paper we consider some four-parametric, so-called Generalized Pareto-like Frequency Distribution, which have been constructed using stochastic Birth-Death Process in order to model phenomena arising in Bioinformatics (Astola and Danielian, 2007). As examples, two ”real data” sets on the number of proteins and number of residues for analyzing such distribution are given. The conditions of coincidence of solution for the system of Likelihood Equations with the Maximum Likelihood Estimators (MLE) for the parameters of this distribution are also investigated. In addition, we propose Accumulation Method as a recurrence method for approximate computation of the MLE of the parameters. Simulation studies are done.Davood FarbodAsymptotic Efficiencies of the MLE Based on Bivariate Record Values from Bivariate Normal Distribution
http://jirss.irstat.ir/browse.php?a_id=231&sid=1&slc_lang=en
Abstract. Maximum likelihood (ML) estimation based on bivariate record data is considered as the general inference problem. Assume that the process of observing k records is repeated m times, independently. The asymptotic properties including consistency and asymptotic normality of the Maximum Likelihood (ML) estimates of parameters of the underlying distribution is then established, when m is large enough. The bivariate normal distribution is considered as an highly applicable example in order to estimate the parameter θ = (μ1, σ1, μ2, σ2) by ML method of estimation based on mk bivariate record data. Asymptotic
variances of the ML estimators are calculated by deriving the Fisher information matrix about θ contained in the vector of the first k bivariate record data. As another application, we concerned the problem of “breaking boards” of Glick (1978, Amer. Math. Monthly, 85, 2-26) by considering three different sampling schemes of breaking boards and we computed the relative asymptotic efficiencies of ML estimators based on these three types of data.Morteza AminiOn Exponential Power Distribution And Poultry Feeds Data: A Case Study
http://jirss.irstat.ir/browse.php?a_id=232&sid=1&slc_lang=en
Abstract. In this paper, we propose to study a generalized form of the exponential power distribution which contains others in the literature
as special cases. This unifying exponential power distribution is characterized
by a parameter ω and a function h(ω) which regulates the tail
behavior of the distribution, thus making it more flexible and suitable
for modeling than the usual normal distribution, while retaining symmetry.
We derive several mathematical and statistical properties of this
distribution and estimate the parameters using both the moments and
maximum likelihood approach, obtaining the information matrix in the
process. The multivariate extension of the distribution is also examined.
Finally we fit the univariate generalized exponential power distribution
as well as the normal distribution to data on eggs produced by chicken
on each of two different poultry feeds (inorganic and organic copper-salt
compositions) and show that the generalized exponential power distribution
fit is considerably better. We then use the Kolmogorov-Smirnov
two samples one-tailed test to show that there is an increase in egg
weights and decrease in cholesterol level when the feed is organic.A. A. OlosundeA Family of Skew-Slash Distributions and Estimation of its Parameters via an EM Algorithm
http://jirss.irstat.ir/browse.php?a_id=233&sid=1&slc_lang=en
Abstract. In this paper, a family of skew-slash distributions is defined and investigated. We define the new family by the scale mixture of a skew-elliptically distributed random variable with the power of a uniform random variable. This family of distributions contains slash-elliptical and skew-slash distributions. We obtain the moments and some distributional properties of the new family of distributions. In the special case of slash skew-t distribution, an EM-type algorithm is presented to estimate the parameters. Some applications are provided for illustrations.R. FarnooshSimulation and Prediction of Wind Speeds: A Neural Network for Weibull
http://jirss.irstat.ir/browse.php?a_id=234&sid=1&slc_lang=en
Abstract. Wind as a resource of renewable energy has obtained an important share of the energy market already. Therefore simulation and prediction of wind speeds is essential for both, for engineers and energy traders.
In this paper we analyze the surface wind speed data from three prototypic locations: coastal region (Rotterdam), undulating forest landscape few 100 m above sea level(Kassel), and alpine mountains about 3000 m above sea level (Zugspitze).
Rather than matching the conventional Weibull distribution to the wind speed data, we investigate two alternative models for wind speed prediction, both being refinements of a log-normal model, but with very different approaches and capability for capturing the extremal events.
In both models deterministic effects such as trend and seasonality are separated. The first (structural stochastic) model predicts wind speeds exponentially from a linear combination of separate mean-reverting jump processes for the high and low wind speed regimes, and the regular (diffusive) wind speed regime. The second (neuro-stochastic) model is a prediction with volatility-enhanced trend, with parameters dynamically learned by the middle-layer neurons of an MLP-type neural network operating on dynamically updated and re-weighted history.
The numerical results suggest that, for a coastal region (e.g. Rotterdam) the R2-determination is higher, while for the undulating forest regions (e.g. Kassel) and even more the higher mountain regions (e.g. Zugspitze) the structural stochastic model yields higher determination.
The neuro-stochastic algorithm opens a new path within statistical learning: feature space and kernel functions are completely defined by the parameters of the stochastic process.Stefan Markus GiebelA GLM-Based Method to Estimate a Copula's Parameter(s)
http://jirss.irstat.ir/browse.php?a_id=235&sid=1&slc_lang=en
Abstract. This study introduces a new approach to problem of estimating parameter(s) of a given copula. More precisely, using the concept of the generalized linear models (GLM) accompanied with least square method, we introduce an estimation method, say GLM-method. A simulation study has been conducted to provide a omparison among the inversion of Kendal’s tau, the inversion of Spearman’s rho, the PML, the Copula-quantile regression with (q = 0:25 0:50 0:75), and the LMmethod. Such simulation study shows that the GLM-method is an appropriate method whenever the data distributed according to an elliptical distribution.Amir Payandeh