Statistics, Optimization & Information Computing http://www.iapress.org/index.php/soic <p><em><strong>Statistics, Optimization and Information Computing</strong></em>&nbsp;(SOIC) is an international refereed journal dedicated to the latest advancement of statistics, optimization and applications in information sciences.&nbsp; Topics of interest are (but not limited to):&nbsp;</p> <p>Statistical theory and applications</p> <ul> <li class="show">Statistical computing, Simulation and Monte Carlo methods, Bootstrap,&nbsp;Resampling methods, Spatial Statistics, Survival Analysis, Nonparametric and semiparametric methods, Asymptotics, Bayesian inference and Bayesian optimization</li> <li class="show">Stochastic processes, Probability, Statistics and applications</li> <li class="show">Statistical methods and modeling in life sciences including biomedical sciences, environmental sciences and agriculture</li> <li class="show">Decision Theory, Time series&nbsp;analysis, &nbsp;High-dimensional&nbsp; multivariate integrals,&nbsp;statistical analysis in market, business, finance,&nbsp;insurance, economic and social science, etc</li> </ul> <p>&nbsp;Optimization methods and applications</p> <ul> <li class="show">Linear and nonlinear optimization</li> <li class="show">Stochastic optimization, Statistical optimization and Markov-chain etc.</li> <li class="show">Game theory, Network optimization and combinatorial optimization</li> <li class="show">Variational analysis, Convex optimization and nonsmooth optimization</li> <li class="show">Global optimization and semidefinite programming&nbsp;</li> <li class="show">Complementarity problems and variational inequalities</li> <li class="show"><span lang="EN-US">Optimal control: theory and applications</span></li> <li class="show">Operations research, Optimization and applications in management science and engineering</li> </ul> <p>Information computing and&nbsp;machine intelligence</p> <ul> <li class="show">Machine learning, Statistical learning, Deep learning</li> <li class="show">Artificial intelligence,&nbsp;Intelligence computation, Intelligent control and optimization</li> <li class="show">Data mining, Data&nbsp;analysis, Cluster computing, Classification</li> <li class="show">Pattern recognition, Computer vision</li> <li class="show">Compressive sensing and sparse reconstruction</li> <li class="show">Signal and image processing, Medical imaging and analysis, Inverse problem and imaging sciences</li> <li class="show">Genetic algorithm, Natural language processing, Expert systems, Robotics,&nbsp;Information retrieval and computing</li> <li class="show">Numerical analysis and algorithms with applications in computer science and engineering</li> </ul> en-US <span>Authors who publish with this journal agree to the following terms:</span><br /><br /><ol type="a"><ol type="a"><li>Authors retain copyright and grant the journal right of first publication with the work simultaneously licensed under a <a href="http://creativecommons.org/licenses/by/3.0/" target="_new">Creative Commons Attribution License</a> that allows others to share the work with an acknowledgement of the work's authorship and initial publication in this journal.</li><li>Authors are able to enter into separate, additional contractual arrangements for the non-exclusive distribution of the journal's published version of the work (e.g., post it to an institutional repository or publish it in a book), with an acknowledgement of its initial publication in this journal.</li><li>Authors are permitted and encouraged to post their work online (e.g., in institutional repositories or on their website) prior to and during the submission process, as it can lead to productive exchanges, as well as earlier and greater citation of published work (See <a href="http://opcit.eprints.org/oacitation-biblio.html" target="_new">The Effect of Open Access</a>).</li></ol></ol> david.iapress@gmail.com (David G. Yu) nhma0004@gmail.com (IAPress technical support) Tue, 26 Jan 2021 12:49:50 +0800 OJS 3.1.2.1 http://blogs.law.harvard.edu/tech/rss 60 Bayesian Online Change Point Detection for Baseline Shifts http://www.iapress.org/index.php/soic/article/view/1072 <p><span class="fontstyle0">In time series data analysis, detecting change points on a real-time basis (online) is of great interest in many areas, such as finance, environmental monitoring, and medicine. One promising means to achieve this is the Bayesian online change point detection (BOCPD) algorithm, which has been successfully adopted in particular cases in which the time series of interest has a fixed baseline. However, we have found that the algorithm struggles when the baseline irreversibly shifts from its initial state. This is because with the original BOCPD algorithm, the sensitivity with which a change point can be detected is degraded if the data points are fluctuating at locations relatively far from the original baseline. In this paper, we not only extend the original BOCPD algorithm to be applicable to a time series whose baseline is constantly shifting toward unknown values but also visualize why the proposed extension works. To demonstrate the efficacy of the proposed algorithm compared to the original one, we examine these algorithms on two real-world data sets and six synthetic data sets.</span></p> Ginga Yoshizawa Copyright (c) 2020 Statistics, Optimization & Information Computing http://www.iapress.org/index.php/soic/article/view/1072 Thu, 03 Dec 2020 00:00:00 +0800 A New Generalized Modified Weibull Distribution http://www.iapress.org/index.php/soic/article/view/1014 <p>We introduce a new distribution, so called A new generalized modified Weibull (NGMW) distribution. Various structural properties of the distribution are obtained in terms of Meijer's $G$--function, such as moments, moment generating function, conditional moments, mean deviations, order statistics and maximum likelihood estimators. The distribution exhibits a wide range of shapes with varying skewness and assumes all possible forms of hazard rate function. The NGMW distribution along with other distributions are fitted to two sets of data, arising in hydrology and in reliability. It is shown that the proposed distribution has a superior performance among the compared distributions as evidenced via goodness--of--fit tests</p> Morad Alizadeh, Muhammad Nauman Khan, Mahdi Rasekhi, G.G Hamedani Copyright (c) 2021 Statistics, Optimization & Information Computing http://www.iapress.org/index.php/soic/article/view/1014 Fri, 22 Jan 2021 00:00:00 +0800 Applications of Some Rating Methods to Solve Multicriteria Decision-Making Problems http://www.iapress.org/index.php/soic/article/view/750 <p>This study proposes a new approach for the solution of multicriteria decision-making problems. The proposed approach is based on using rating/ranking methods. Particularly, in this paper, we investigate the possibility of applying Massey, Colley, Keener, offence-defence, and authority-hub rating methods, which are successfully used in various fields. The proposed approach is useful when no decision-making authority is available or when the relative importance of various criteria has not been previously evaluated. The proposed approach is tested with an example problem to demonstrate its viability and suitability for&nbsp; application.</p> Joseph Gogodze Copyright (c) 2020 Statistics, Optimization & Information Computing http://www.iapress.org/index.php/soic/article/view/750 Thu, 24 Dec 2020 00:00:00 +0800 Inferences for Weibull parameters under progressively first-failure censored data with binomial random removals http://www.iapress.org/index.php/soic/article/view/611 In this paper, the Bayesian and non-Bayesian estimation of a two-parameter Weibull lifetime model in presence of progressive first-failure censored data with binomial random removals are considered. Based on the s-normal approximation to the asymptotic distribution of maximum likelihood estimators, two-sided approximate confidence intervals for the unknown parameters are constructed. Using gamma conjugate priors, several Bayes estimates and associated credible intervals are obtained relative to the squared error loss function. Proposed estimators cannot be expressed in closed forms and can be evaluated numerically by some suitable iterative procedure. A Bayesian approach is developed using Markov chain Monte Carlo techniques to generate samples from the posterior distributions and in turn computing the Bayes estimates and associated credible intervals. To analyze the performance of the proposed estimators, a Monte Carlo simulation study is conducted. Finally, a real data set is discussed for illustration purposes. Samir K. Ashour, Ahmed A. El-Sheikh, Ahmed Elshahhat Copyright (c) 2020 Statistics, Optimization & Information Computing http://www.iapress.org/index.php/soic/article/view/611 Thu, 18 Jun 2020 00:00:00 +0800 The Weibull Birnbaum-Saunders Distribution And Its Applications http://www.iapress.org/index.php/soic/article/view/887 <p>A new lifetime model, with four positive parameters, called the Weibull Birnbaum-Saunders distribution is proposed. The proposed model extends the Birnbaum-Saunders distribution and provides great flexibility in modeling data in practice. Some mathematical properties of the new distribution are obtained including expansions for the cumulative and density functions, moments, generating function, mean deviations, order statistics and reliability. Estimation of the model parameters is carried out by the maximum likelihood estimation method. A simulation study is presented to show the performance of the maximum likelihood estimates of the model parameters. The flexibility of the new model is examined by applying it to two real data sets.</p> Lazhar BENKHELIFA Copyright (c) 2020 Statistics, Optimization & Information Computing http://www.iapress.org/index.php/soic/article/view/887 Tue, 23 Jun 2020 00:00:00 +0800 Comparison of two sampling schemes in estimating the stress-strength reliability under the proportional reversed hazard rate model http://www.iapress.org/index.php/soic/article/view/781 In this paper, point and interval estimation of stress-strength reliability based on lower record ranked set sampling scheme under the proportional reversed hazard rate model are considered. Maximum likelihood, uniformly minimum variance unbiased, and Bayesian estimators of $\mathcal{R}$ are derived and their performances are compared. Various confidence intervals for the parameter $\mathcal{R}$ are constructed, and compared based on the simulation study. Moreover, the record ranked set sampling scheme is compared with ordinary records in case of interval estimations. Finally, a data set has been analyzed for illustrative purposes. Amineh Sadeghpour, Ahmad Nezakati, Mahdi Salehi Copyright (c) 2020 Statistics, Optimization & Information Computing http://www.iapress.org/index.php/soic/article/view/781 Tue, 30 Jun 2020 00:00:00 +0800 Estimation and Testing Procedures for the Reliability Characteristics of Chen Distribution Based on Type II Censoring and the Sampling Scheme of Bartholomew http://www.iapress.org/index.php/soic/article/view/1032 <p>In this paper, we consider Chen distribution and derive UMVUEs and MLEs of the parameter&nbsp;λ , hazard rate h(t) and the two measures of reliability, namely R(t) = P(X &gt; t), where X denotes the lifetime of an item and P = P(X &gt; Y ), which represents the reliability of an item or system of random strength X subject to random stress Y , under type II censoring scheme and the sampling scheme of Bartholomew . We also develop interval estimates of the reliability measures. Testing procedures for the hypotheses related to different parametric functions have also been developed. A comparative study of different methods of point estimation and average con ddence length has been done through simulation studies. The analysis of a real data set is presented for illustration purpose.</p> Aditi chaturvedi, Surinder Kumar Copyright (c) 2020 Statistics, Optimization & Information Computing http://www.iapress.org/index.php/soic/article/view/1032 Mon, 07 Dec 2020 00:00:00 +0800 A New Generalized Cauchy Distribution with an Application to Annual One Day Maximum Rainfall Data http://www.iapress.org/index.php/soic/article/view/1000 <p>In this article, we introduce a new three-parameter transmuted Cauchy distribution using<br>the quadratic rank transmutation map approach. Some mathematical properties of the pro-<br>posed model are discussed. A simulation study is conducted using the method of maximum<br>likelihood estimation to estimate the parameters of the proposed model. We used two real data<br>sets and compare various statistics to show the fitting and versatility of the model.</p> Cory Ball, Binod Rimal, Sher Chhetri Copyright (c) 2021 Statistics, Optimization & Information Computing http://www.iapress.org/index.php/soic/article/view/1000 Sat, 09 Jan 2021 00:00:00 +0800 Hierarchical Forecasting of the Zimbabwe International Tourist Arrivals http://www.iapress.org/index.php/soic/article/view/959 <p>The objectives of the paper is to: (1) adopt the hierarchical forecasting methods in modelling and forecasting international tourist arrivals in Zimbabwe; and (2) coming up with Zimbabwe international tourist arrivals Prediction Intervals (PIs) in Quantile Regression Averaging (QRA) to hierarchical tourism forecasts. Zimbabwe’s monthly international tourist arrivals data from January 2002 to December 2018 was used. The dataset used was before the COVID-19 period and were disaggregated according to the purpose of the visit (POV). Three hierarchical forecasting approaches, namely top-down, bottom-up and optimal combination approaches were applied to the data. The results showed the superiority of the bottom-up approach over both the top-down and optimal combination approaches. Forecasts indicate a general increase in aggregate series. The combined methods provide a new insight into modelling tourist arrivals. The approach is useful to the government, tourism stakeholders, and investors among others, for decision-making, resource mobilisation and allocation. The Zimbabwe Tourism Authority (ZTA) could adopt the forecasting techniques to produce informative and precise tourism forecasts. The data set used is before the COVID-19 pandemic and the models indicate what could happen outside the pandemic. During the pandemic the country was under lockdown with no tourist arrivals to report on. The models are useful for planning purposes beyond the COVID-19 pandemic.</p> Tendai Makoni, Delson Chikobvu, Caston Sigauke Copyright (c) 2021 Statistics, Optimization & Information Computing http://www.iapress.org/index.php/soic/article/view/959 Wed, 20 Jan 2021 00:00:00 +0800 Testing the Number of Components in a Birnbaum-Saunders Mixture Model under a Random Censoring Scheme http://www.iapress.org/index.php/soic/article/view/919 <p>This paper deals with testing the number of components in a Birnbaum-Saunders mixture model under randomly right censored data. We focus on two methods, one based on the modified likelihood ratio test and the other based on the shortcut of bootstrap test. Based on extensive Monte Carlo simulation studies, we evaluate and compare the performance of the proposed tests through their size and power. A power analysis provides guidance for researchers to examine the factors that affect the power of the proposed tests used in detecting the correct number of components in a Birnbaum-Saunders mixture model. Finally an example of aircraft Windshield data is used to illustrate the testing procedure.</p> Walaa EL-Sharkawy, Moshira A. Ismail Copyright (c) 2021 Statistics, Optimization & Information Computing http://www.iapress.org/index.php/soic/article/view/919 Fri, 15 Jan 2021 00:00:00 +0800 System Maintenance Using Several Imperfect Repairs Before a Perfect Repair http://www.iapress.org/index.php/soic/article/view/861 <p>Allowing several imperfect repairs before a perfect repair can lead to a highly reliable and efficient system by reducing repair time and repair cost. Assuming exponential lifetime and exponential repair time, we determine the optimal probability $p$ of choosing a perfect repair over an imperfect repair after each failure. Based on either the limiting availability or the limiting average repair cost per unit time, we determine the optimal number of imperfect repairs before conducting a perfect repair.</p> Haixia Smithson, Jyotirmoy Sarkar Copyright (c) 2021 Statistics, Optimization & Information Computing http://www.iapress.org/index.php/soic/article/view/861 Fri, 22 Jan 2021 00:00:00 +0800 A flexible ranked set sampling schemes: Statistical analysis on scale parameter http://www.iapress.org/index.php/soic/article/view/812 <p>A flexible ranked set sampling scheme including some various existing sampling methods&nbsp; is proposed. This scheme may be used to minimize the&nbsp; error of ranking and the cost of sampling. Based on the data obtained from this scheme, the maximum likelihood estimation as well as the Fisher information are studied for the&nbsp; scale family of distributions. The existence and uniqueness of&nbsp; the&nbsp; maximum likelihood estimator&nbsp; of the scale parameter of the exponential&nbsp; and&nbsp; normal distributions are&nbsp; investigated. Moreover, the optimal scheme is derived via simulation and numerical computations.</p> Abbas Eftekharian, Mostafa Razmkhah, Jafar Ahmadi Copyright (c) 2020 Statistics, Optimization & Information Computing http://www.iapress.org/index.php/soic/article/view/812 Wed, 01 Jul 2020 00:00:00 +0800 Modelling Crude Oil Returns Using the NRIG Distribution http://www.iapress.org/index.php/soic/article/view/1025 <p>Over the past decade, crude oil prices have risen dramatically, making the oil market very volatile and risky; hence, implementing an efficient risk management tool against market risk is crucial. Value-at-risk (VaR) has become the most common tool in this context to quantify market risk. Financial data typically have certain features such as volatility clustering, asymmetry, and heavy and semi-heavy tails, making it hard, if not impossible, to model them by using a normal distribution. In this paper, we propose the subclasses of the generalised hyperbolic distributions (GHDs), as appropriate models for capturing these characteristics for the crude oil and gasoline returns. We also introduce the new subclass of GHDs, namely normal reciprocal inverse Gaussian distribution (NRIG), in evaluating the VaR for the crude oil and gasoline market. Furthermore, VaR estimation and backtesting procedures using the Kupiec likelihood ratio test are conducted to test the extreme tails of these models. The main findings from the Kupiec likelihood test statistics suggest that the best GHD model should be chosen at various VaR levels. Thus, the final results of this research allow risk managers, financial analysts, and energy market academics to be flexible in choosing a robust risk quantification model for crude oil and gasoline returns at their specific VaR levels of interest. Particularly for NRIG, the results suggest that a better VaR estimation is provided at the long positions.</p> Knowledge Chinhamu , Nompilo Mabaso, Retius Chifurira Copyright (c) 2020 Statistics, Optimization & Information Computing http://www.iapress.org/index.php/soic/article/view/1025 Thu, 24 Dec 2020 00:00:00 +0800 The Impact of International Trade on Central Bank Efficiency: An Application of DEA and Tobit Regression Analysis http://www.iapress.org/index.php/soic/article/view/1077 <p>The purpose of this study is to introduce a novel methodology to measure the central bank efficiency. The data envelopment analysis (DEA) applies in the combination of three input and two output variables characterizing the economic balance in international trade. &nbsp;Super-efficiency DEA model is applied for ranking &amp; comparing the efficiency of different central banks. In contrast, the Malmquist productivity index (MPI) is used to measure the productivity change over the period of time. Further, the study is extended to quantify the impact of international trade dimension on the efficiency of the central bank by using Tobit regression analysis. Finally, based on our data analysis, we reported that the efficiency changes over the period of time and the total productivity changes significantly due to the technology shift as compared to efficiency change. Additionally, it is also observed that the central bank efficiency is impacted dramatically by the export level of the country as compared to import level, average exchange rate and GDP. It implies that the export level of the country significantly influences the performances of the central bank.</p> Qaiser Farooq Dar, Young-Hyo Ahn, Gulbadin Farooq Dar Copyright (c) 2021 Statistics, Optimization & Information Computing http://www.iapress.org/index.php/soic/article/view/1077 Fri, 22 Jan 2021 00:00:00 +0800 Random Polygons and Optimal Extrapolation Estimates of pi http://www.iapress.org/index.php/soic/article/view/1193 <p>We construct optimal extrapolation estimates of π based on random polygons generated by n independent points uniformly distributed on a unit circle in R2. While the semiperimeters and areas of these random n-gons converge to π almost surely and are asymptotically normal as n → ∞, in this paper we develop various extrapolation processes to further accelerate such convergence. By simultaneously considering the random n-gons and suitably constructed random 2n-gons and then optimizing over functionals of the semiperimeters and areas of these random polygons, we derive several new estimates of π with faster convergence rates. These extrapolation improvements are also shown to be asymptotically normal as n → ∞.</p> Shasha Wang, Wen-Qing Xu, Jitao Liu Copyright (c) 2021 Statistics, Optimization & Information Computing http://www.iapress.org/index.php/soic/article/view/1193 Sun, 28 Mar 2021 10:16:09 +0800