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Öğe Circular success and failure runs in a sequence of exchangeable binary trials(Elsevier Science Bv, 2013) Atalay, Sevcan Demir; Zeybek, MelisLet X-1, ... , X-n be an exchangeable sequence of binary trials arranged on a circle with possible values "1" (success) or "0" (failure). In an exchangeable sequence, the joint distribution of X-1,X-2, ... ,X-n is invariant under the permutation of its arguments. For the circular sequence, general expressions for the joint distributions of run statistics based on the joint distribution of success and failure run lengths are obtained. As a special case, we present our results for Bernoulli trials. The results presented consist of combinatorial terms and therefore provide easier calculations. For illustration purposes, some numerical examples are given and the reliability of the circular combined k-out-of-n:G and consecutive k(c)-out-of-n:G system under stress-strength setup is evaluated. (C) 2012 Elsevier B.V. All rights reserved.Öğe Circular success and failure runs in a sequence of exchangeable binary trials(Elsevier Science Bv, 2013) Atalay, Sevcan Demir; Zeybek, MelisLet X-1, ... , X-n be an exchangeable sequence of binary trials arranged on a circle with possible values "1" (success) or "0" (failure). In an exchangeable sequence, the joint distribution of X-1,X-2, ... ,X-n is invariant under the permutation of its arguments. For the circular sequence, general expressions for the joint distributions of run statistics based on the joint distribution of success and failure run lengths are obtained. As a special case, we present our results for Bernoulli trials. The results presented consist of combinatorial terms and therefore provide easier calculations. For illustration purposes, some numerical examples are given and the reliability of the circular combined k-out-of-n:G and consecutive k(c)-out-of-n:G system under stress-strength setup is evaluated. (C) 2012 Elsevier B.V. All rights reserved.Öğe Confidence Interval based Quality Improvement for Non-normal Responses(2019) Zeybek, MelisRobust parameter design is an effective tool to determine the optimal operating conditions of a system. Because of its practicability and usefulness, the widespread applications of robust design techniques provide major quality improvements. the usual assumptions of robust parameter design are that normally distributed experimental data and no contamination due to outliers. Optimizing an objective function under the normality assumption for a skewed data in dual-response modeling may result in misleading fit and operating conditions located far from the optimal values. This creates a chain of degradation in the production phase, e.g., poor quality products. This paper focuses on skewed experimental data. the proposed approach is constructed on the confidence interval of the process mean which makes the system median unbiased for the mean using the skewness information of the data. the response modeling of the midpoint of the interval is proposed as a location performance response. the main advantages of the proposed approach are that it gives a robust solution due to the skewed structure of the experimental data distribution and does not need any transformation which causes any loss of information in estimation of the mean response. the procedure and the validity of the proposed approach are illustrated on a popular example, the printing process study.Öğe Öğe Do CMT, SCC, and Bacteriological isolation overlap in subclinical mastitis cases of Anatolian buffaloes?(2023) Zeybek, Melis; Goncagül, Gülşen; Lısuzzo, Anastasia; Fıore, Enrico; Çokal, Yavuz; Günaydın, ElçinSubclinical mastitis is the most important and costly disease in the dairy sector. In this study, it was aimed to compare the results of bacteriological examination with those of California Mastitis Test (CMT) and Somatic Cell Count (SCC)in the milk samples collected from Anatolian buffaloes with no clinical signs of mastitis. For this purpose, 96 milk samples were collected from 24 Anatolian buffaloes of each quarter. All milk samples were examined for the presence of mastitic pathogens by bacteriology regardless of SCC values and CMT scores. A total of 103 isolates were recovered from the infected quarters. The first three frequently isolated mastitic pathogens were determined to be E. coli, S. agalactiae, and S. aureus with the rate of 31.07%, 22.33%, and 21.36%, respectively. According to the bacteriology results, threshold value for SCC was accepted as ?78.000 cells/ml. The correlation value between CMT and SCC, CMT and bacteriology, and SCC and bacteriology was found as 0.737, 0.845 and 0.872, respectively, and the mean of inter-item correlation was determined 0.818. These results showed that the test results were highly correlated with each other. The results of the ROC analysis of the cut-of-value of the SCC test for this study chosen as 78.000 cells/ml supported the results obtained from the reliability analysis with sensitivity 85% and 1-specifity 100%. To sum up, a combination of CMT, SCC, and bacteriological investigation provides benefits in detecting mastitis early and avoiding misdiagnosis, allowing for timely action and treatment.Öğe Dual Response Surface Optimization Based on Skill Scores(Univ Kebangsaan Malaysia, Fac Science & Technology, 2024) Kozan, Agah; Zeybek, Melis; Kozan, ElifThe popular formulations of dual -response optimization are constructed on minimizing a function of bias and system variability. This study provides an opportunity to evaluate the dual response surface ( DRS ) problem from a different perspective by adapting two new terms such that internal and external quality forecasts. The background of the proposed approach focuses on the relationship between internal and external quality forecasts and discusses the DRS problem in regards of skill scores by defining a model quality criterion. Skill is the relative accuracy of the forecast and defines a correspondence between forecast of interest and reference forecasts. The reference forecast does not require any knowledge or modelling; thus, it is an unskilled forecast. In this context, skill score is a measure of this relative improvement and widely used in evaluating the performance of operational and experimental forecasts. An alternative version of mean square error ( MSE ) which is reconstructed by skill scores and model quality criterion is proposed as an objective function for the DRS problem. Integrating the relationship between internal and external quality forecasts into such a response function can improve the effectiveness and cooperation of the applied technique. The proposed approach has a flexible structure and provides decision makers alternative solutions for different values of the model quality criterion. The proposed procedure is discussed by conducted a simulation study and demonstrated in an engineering process.Öğe A dual-response surface modeling approach for gamma robust design(Wiley, 2020) Zeybek, Melis; Koksoy, Onur; Robinson, Timothy J.Robust parameter design is a methodology that involves experimental design and strategic modeling for the purpose of simultaneously reducing system variability while achieving a target specification for the system mean. Modeling results obtained under unrealistic assumptions about the underlying data distribution may mislead practitioners when it comes to improving system quality. Using classical normal theory modeling techniques for right-skewed experimental data in dual-response modeling has some drawbacks, such as obtaining a misleading fit and estimated optimal operating conditions that are potentially far from the true optimal values. Moreover, using inappropriate modeling methods can create a chain of degradation in the production phase and subsequently result in poor system performance. This paper proposes a new dual-response surface modeling approach when the quality characteristic of a system follows a gamma distribution. the procedure and its advantages are illustrated using the well-known printing process experiment.Öğe The effects of gamma noise on quality improvement(Taylor & Francis Inc, 2020) Zeybek, Melis; Koksoy, OnurTaguchi's robust parameter design is an experimental procedure based on reducing the system variability that noise factors cause. the results, obtained under unrealistic assumptions about noise, may mislead practitioners when it comes to improving quality in robust design. For example, many hydrological data and the multi-path fading of a signal in wireless communication systems are positively skewed and cannot be modeled by any normal distribution. This manuscript focuses on the case where noise factor follows gamma distribution and investigates its true effects on the following: the response, the choice of an estimator in modeling, and the estimation of optimum factor settings. Then, a new density function is proposed for a given response under the gamma effect. A design of simulated experiments with gamma noise is conducted and two related examples are presented to illustrate the findings.Öğe AN EFFICIENT LOSS FUNCTION APPROACH TO OPTIMIZE CORRELATED MULTI-RESPONSES(Univ Cincinnati Industrial Engineering, 2019) Koksoy, Onur; Zeybek, MelisIn quality engineering, engineering intuition is often ineffective and inconclusive for interpreting the behaviors of quality characteristics and their possible effects on process loss. Loss functions can be utilized in process design and optimization by aligning losses in a way which minimizes expected losses, even when responses are correlated and losses are the result of co-movements of those responses, i.e., synergy or antagonism of loss. Most of the current literature on multidimensional quality does not provide enough information about the effects of responses moving simultaneously in the same/opposite direction on process loss. To fill this gap, this manuscript focuses on co-movement effects and provides an efficient approach based on multivariate upside-down normal loss function. the procedure and its advantages are illustrated by an example.Öğe An efficient loss function approach to optimize correlated multi-responses(2019) Köksoy, Onur; Zeybek, Melis…Öğe The First Detection of anti-Anaplasma phagocytophilum Antibodies in Horses in Turkey(2018) Günaydın, Elçin; Pekkaya, Selçuk; Kuzugüden, Fatih; Zeybek, Melis; Gökmen, Tülin Güven; Ütük, Armağan ErdemAnaplasma phagocytophilum, the causative agent of equine granulocytic anaplasmosis, affects several species of wild and domesticated mammals, including horse, besides human. In Turkey, there were many reports on A. phagocytophilum circulation among cattles, sheep, dogs, mice, humans, except horses. In this study, we aimed to inquiry whether A. phagocytophilum were circulating among the horse population or not. For this purpose, 105 mare horse blood sera were examined for the presence of Anti-Anaplasma phagocytophilum IgG antibodies by IFAT. The seroprevalance rate of 8.57% horse sera were found to be positive. This was the first report about the presence of anti-A. phagocytophilum antibodies in horses in Turkey..Öğe Öğe Öğe INTERVAL ROBUST DESIGN ON QUALITY IMPROVEMENT FOR N ON-NORMAL AND CONTAMINATED RESPONSES(University Cincinnati Industrial Engineering, 2024) Baydar, Atakan; Zeybek, Melis; Kozan, Elif; Kozan, AgahThe basis of robust parameter design is the creation of a design that can resist the negative effects caused by uncontrollable or difficult-to-control external and environmental factors, which affect the product parameters in achieving product design during product realization activities. Robustness is the ability of a product or process to be least affected by variabilities caused by external factors. The success of the response surface methodology generally depends on a model chosen to fit the data distribution. Making incorrect assumptions regarding data distribution when creating response surface models can affect the effectiveness of the quality improvement strategy used. Non-normal or contaminated data is a common phenomenon in quality improvement applications. Although non-normal data is common in robust parameter applications, it is often the case that users ignore the underlying distribution shape of the data at the modeling stage and use normal theory techniques naively. This study proposes a dual response surface approach based on robust confidence intervals for cases where the experimental data do not meet normality assumptions or have contaminated data distribution. A new dual response surface methodology is proposed based on modeling the MAD - t confidence interval, S-n - t confidence interval, and Q(n) - t confidence interval formulations with the response surface methodology. All the proposed methods make the process median unbiased for the mean using the skewness of the experimental data. Two well-known experimental design studies are used to demonstrate the procedure and its advantages.Öğe Interval robust design under contaminated and non normal data(Taylor & Francis Inc, 2020) Zeybek, MelisRobust parameter design (RPD) is an effective tool, which involves experimental design and strategic modeling to determine the optimal operating conditions of a system. the usual assumptions of RPD are that normally distributed experimental data and no contamination due to outliers. and generally the parameter uncertainties in response models are neglected. However, using normal theory modeling methods for a skewed data and ignoring parameter uncertainties can create a chain of degradation in optimization and production phases such that misleading fit, poor estimated optimal operating conditions, and poor quality products. This article presents a new approach based on confidence interval (CI) response modeling for the process mean. the proposed interval robust design makes the system median unbiased for the mean and uses midpoint of the interval as a measure of location performance response. As an alternative robust estimator for the process variance response modeling, using biweight midvariance is proposed which is both resistant and robust of efficiency where normality is not met. the results further show that the proposed interval robust design gives a robust solution to the skewed structure of the data and to contaminated data. the procedure and its advantages are illustrated using two experimental design studies.Öğe Kayıp fonksiyonlarına dayalı süreç-dışı kalite geliştirme yaklaşımları(Ege Üniversitesi, Fen Bilimleri Enstitüsü, 2015) Zeybek, Melis; Köksoy, OnurBu tezde gürültü değişkenlerinin olasılık dağılımının sağa çarpık bir yapıda olan gamma dağılımına uygunluğu varsayımı altında kalite geliştirme yaklaşımları çalışılmıştır. Önerilen yaklaşımlar kapsamında, ilk olarak gürültü değişkenlerinin gamma dağılımına sahip olduğu varsayımı altında, yanıtların olasılık yoğunluk fonksiyonu elde edilmiştir. Ayrıca, yeni bir asimetrik kayıp fonksiyonu tanıtılmıştır ve özellikleri incelenmiştir. Son olarak, önerilen asimetrik kayıp fonksiyonu da göz önünde bulundurularak, yanıtların elde edilen olasılık yoğunluk fonksiyonuna uygunluğu varsayımı altında geliştirilen yeni bir ikili yanıt yüzey yaklaşımına yer verilmiştir. Gamma dağılımına sahip gürültü değişkenlerinin deney sırasında rasgele değer aldıkları varsayımı altında yapılan simülasyon çalışması ile bir deney tasarımı oluşturulmuştur ve yanıtların dağılımı incelenerek teorik olarak elde edilen olasılık yoğunluk fonksiyonuna uygunluğu gösterilmiştir. Önerilen kayıp fonksiyonu kullanılarak noktasal kayıplar tespit edilmiştir ve önerilen ikili yanıt yüzey yaklaşımının bir uygulaması yapılmıştır.Öğe Kayıp fonksiyonlarına dayalı süreç-dışı kalite geliştirme yaklaşımları(Ege Üniversitesi, 2015) Zeybek, Melis; Köksoy, OnurBu projede, gürültü değişkenlerinin olasılık dağılımının sağa çarpık bir yapıda olan gamma dağılımına uygunluğu varsayımı altında kalite geliştirme yaklaşımları çalışılmıştır. Önerilen yaklaşımlar kapsamında, ilk olarak gürültü değişkenlerinin gamma dağılımına sahip olduğu varsayımı altında, yanıtların olasılık yoğunluk fonksiyonu elde edilmiştir. Ayrıca, yeni bir asimetrik kayıp fonksiyonu tanıtılmıştır ve özellikleri incelenmiştir. Son olarak, önerilen asimetrik kayıp fonksiyonu da göz önünde bulundurularak, yanıtların elde edilen olasılık yoğunluk fonksiyonuna uygunluğu varsayımı altında geliştirilen yeni bir ikili yanıt yüzey yaklaşımına yer verilmiştir. Gamma dağılımına sahip gürültü değişkenlerinin deney sırasında rasgele değer aldıkları varsayımı altında yapılan simülasyon çalışması ile bir deney tasarımı oluşturulmuştur ve yanıtların dağılımı incelenerek teorik olarak elde edilen olasılık yoğunluk fonksiyonuna uygunluğu gösterilmiştir ve önerilen ikili yanıt yüzey yaklaşımının bir uygulaması yapılmıştır.;Off-line quality control, Dual response surface approach, Asymmetric loss function.;Süreç-dışı kalite kontrol, İkili yanıt yüzey yaklaşımı, Asimetrik kayıp fonksiyonu.Öğe The modified maximum likelihood estimators for the parameters of the regression model under bivariate median ranked set sampling(Springer Heidelberg, 2022) Sazak, Hakan Savas; Zeybek, MelisWe derived the modified maximum likelihood (MML) regression type estimators using bivariate median ranked set sampling (MRSS) and conducted an extensive simulation study to compare them with their least squares (LS) counterparts using MRSS and with the MML and LS counterparts using ranked set sampling (RSS). Under normality, the MML estimators using bivariate MRSS are mostly better than the LS estimators using bivariate MRSS in most of the situations, especially when the correlation between the concomitant and primary variables is high. In general, MRSS is superior to RSS in the estimation of the location parameters of the concomitant and primary variables. In the estimation of the other parameters, RSS is superior to MRSS and the MML estimators using RSS are mostly the best estimators of all. For Weibull distribution, the LS estimators using MRSS are mostly better than the MML estimators using MRSS but in general, the MML estimators using RSS are the superior estimators among all, especially for higher cycles. At the end of the study, we give two examples illustrating the procedures and merits of the newly proposed estimators.Öğe The modified maximum likelihood regression type estimators using bivariate ranked set sampling(Taylor & Francis Inc, 2019) Sazak, Hakan Savas; Zeybek, MelisRank set sampling (RSS) is an efficient sampling technique, used especially in the situations where the measurement on the variable of interest is time-consuming, costly or difficult. One of the modifications to make it more efficient is the regression type estimation using bivariate RSS. We derive the modified maximum likelihood (MML) regression type estimators using bivariate RSS when the concomitant variable X is stochastic and the error term is non-normal where it is problematic to obtain the maximum likelihood (ML) estimators. The procedures and merits of the proposed estimators are illustrated through simulations and two real-life applications.Öğe The modified maximum likelihood regression type estimators using bivariate ranked set sampling(Taylor & Francis Inc, 2021) Sazak, Hakan Savas; Zeybek, MelisRank set sampling (RSS) is an efficient sampling technique, used especially in the situations where the measurement on the variable of interest is time-consuming, costly or difficult. One of the modifications to make it more efficient is the regression type estimation using bivariate RSS. We derive the modified maximum likelihood (MML) regression type estimators using bivariate RSS when the concomitant variable X is stochastic and the error term is non-normal where it is problematic to obtain the maximum likelihood (ML) estimators. The procedures and merits of the proposed estimators are illustrated through simulations and two real-life applications.
