Quantile regression is one of the alternative regression techniques used when the assumptions of classical regression analysis are not met, and it estimates the values of the study variable in various quantiles of the distribution. This study proposes ratio-type estimators of a population mean using the information on quantile regression for stratified random sampling. The proposed ratio-type estimators are investigated with the help of the mean square error equations. Efficiency comparisons between the proposed estimators and classical estimators are presented in certain conditions. Under these obtained conditions, it is seen that the proposed estimators outperform the classical estimators. In addition, the theoretical results are supported by a real data application.

The geographically weighted regression (GWR) model is a local spatial regression technique used to determine and map spatial variations in the relationships between variables. In the GWR model, the bandwidth is very important as it can change the parameter estimates and affect the model performance. In this study, we applied the information complexity (ICOMP) type criteria in the selection of fixed bandwidth for the first time in the literature. The ICOMP‐type criteria use a complexity measure that measures how parameters in the model relate to each other. A real dataset example and a simulation study have been conducted. Results of the simulation demonstrate that GWR models created with the bandwidth selection by ICOMP‐type criteria show superior performance. In addition, when the bandwidth is selected according to the ICOMP‐type criteria and the GWR model is created for the actual total fertility rate data, it is seen that the spatial distribution of the total fertility rate estimates is quite compatible with the distribution of the actual total fertility rate. According to the results, ICOMP‐type criteria can be used effectively instead of the classical criteria in the literature in the selection of bandwidth in the GWR model.

The negative binomial regression model is a widely adopted approach when dealing with dependent variables that consist of non-negative integers or counts. This model serves as an alternative regression technique for addressing issues related to overdispersion in count data. Typically, the maximum likelihood estimator is employed to estimate the parameters of the negative binomial regression model. However, the maximum likelihood estimator can be highly sensitive to multicollinearity, leading to unreliable results. To eliminate the adverse effects of multicollinearity in the negative binomial regression model, we propose the use of a jackknife version of the Kibria–Lukman estimator. In this study, we conducted a theoretical comparison between the proposed jackknife Kibria–Lukman negative binomial regression estimator and several existing estimators documented in the literature. To assess the performance of the proposed estimator, we conducted two simulation studies and performed a real data application. The results from both the simulation studies and the real data application consistently demonstrated that the proposed jackknife Kibria–Lukman negative binomial regression estimator outperforms other estimators.

High-dimensional data sets frequently occur in several scientific areas, and special techniques are required to analyze these types of data sets. Especially, it becomes important to apply a suitable model in classification problems. In this study, a novel approach is proposed to estimate a statistical model for high-dimensional data sets. The proposed method uses analytical hierarchical process (AHP) and information criteria for determining the optimal PCs for the classification model. The high-dimensional colon and gravier datasets were used in evaluation part. Application results demonstrate that the proposed approach can be successfully used for modeling purposes.

Obesity is a growing public health concern, particularly among university students who are exposed to lifestyle changes, disordered eating habits, and reduced physical activity. The aim of this study is to classify obesity risk levels among university students using machine learning classification methods and to identify the most influential factors associated with this risk. The study sample consisted of data collected from 445 students studying at Çankırı Karatekin University. In this context, eight machine learning algorithms—Logistic Regression, Random Forest, Extra Trees, Support Vector Machines, K-Nearest Neighbor, Quadratic Discriminant Analysis, Naive Bayes, and Multilayer Perceptron—were compared to classify obesity risk. Class imbalance in the dataset was addressed using the Adaptive Synthetic Sampling (ADASYN) method applied exclusively to the training set. The models were evaluated using standard performance metrics, and the highest accuracy rate (96.26%) was achieved by the Random Forest model, followed by Logistic Regression with 94.77% accuracy. Variable importance analysis indicated that age, internet use scale score, and fast-food consumption frequency were the most influential factors in classification, while the low correlation between variables (|r| < 0.2) suggested that model performance was driven by the combined contribution of multiple features. Overall, the findings demonstrate that the balanced machine learning approach, particularly ensemble-based methods, can classify obesity risk with high accuracy and provide valuable insights for targeted prevention strategies among university students.