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    Comparison of Different Unidimensional-CAT Algorithms Measuring Students' Language Abilities: Post-hoc Simulation Study
    (Future Acad, 2016) Ozdemir, Burhanettin
    The purpose of this study is to examine the applicability of Computerized Adaptive Testing (CAT) for English Proficiency Tests (EPT) and to determine the most suitable unidimensional-CAT algorithm that aims to measure language ability of university students. In addition, results of CAT designs were compared to the results of the original paper-pencil format of EPT. For this purpose, real data set was used to create item pool. In order to determine the best CAT algorithm for EPT, three different theta estimation methods, three different Fisher-information based item selection methods and four different Kullback-Leibler divergence based item selection methods and three different termination methods were used. In total, 63 different conditions were taken into consideration and results of these conditions were compared with respect to SEM, averaged number of administered items, reliability coefficients and RMSD values between full bank theta and estimated CAT theta. Results indicated that using different theta estimation methods and item selection methods and termination rules had substantial effect on SEM of estimated theta, averaged number of administered items and RMSD values. Averaged number of administered items decreased to less than 11 items when precision criteria to terminate the analysis was set to.30. Overall, EAP estimation method with Fixed pointwise Kullback-Leibler (FP-KL) item selection and precision based stopping rule (0.20) yield more consistent results with smaller RMSD and SEM. Results indicated that post-hoc CAT simulation for EPT provided ability estimations with higher reliability and fewer items compared to corresponding paper and pencil format. (C) 2016 Published by Future Academy www.FutureAcademy.org.uk
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    Examining the Effect of Content Balancing on Multidimensional Computerized Adaptive Testing Based on Between-Item Dimensionality Model
    (Assoc Measurement & Evaluation Education & Psychology, 2015) Ozdemir, Burhanettin; Gelbal, Selahattin
    The purpose of this study is to compare the performance of Between-item dimensionality-based Multidimensional CAT designs and to examine the effect of content balancing on different MCAT designs. For this purpose, real data set obtained from English Proficiency Test (EPT), which was administered by Hacettepe University between 2009 and 2013 academic years, was used. The three dimensional item pool consisted of real items measuring students' listening, grammar and reading abilities. Item pool consisted of 555 items which was calibrated with 2PL between-item MIRT model. In this study, two different theta estimation (Fisher scoring and Bayesian MAP) methods, three different fisher information based item selection methods (A-optimality, D-optimality and Random) and three different precision based termination methods were used in order to determine the best MCAT design. In addition, results of MCAT algorithms with content distribution and without content distribution were compared so as to examine the effect of content balancing in the context of MCAT. The results of each MCAT condition were compared with respect to, reliability index, SEM, RMSD values associated with each dimension. According to results, both Bayesian MAP and Fisher's scoring methods yielded similar results when A-Optimality item selection method was used. However, Fisher's scoring method appeared to be affected from item selection methods and content balancing. Moreover, average number of items tended to increase and reliability coefficients tended to decrease somewhat, while standard error and RMSD values tended to decrease when content balancing was applied in MCAT.
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    Examining the Factors of Self-Compassion Scale with Canonical Commonality Analysis: Syrian Sample
    (Ani Yayincilik, 2017) Ozdemir, Burhanettin; Seef, Nesrin
    Purpose of Study: The purpose of this study is to examine the psychological structure of self-compassion and to determine the relationship between the sub-dimensions (or factors) of the self-compassion-scale and the contribution of each factor to the construct. Although the self-compassion scale has been commonly used in the area of psychology, the number of the studies that examine the relationship between the factors (or sub-dimensions) of self-compassion is limited. The contribution of this study is assumed to be substantial since it examines the relationship between the several factors of self-compassion and determines the unique and common contribution of each factor to the self-compassion construct. Method: This study employed a relational survey method. A purposive sampling technique was used in order to determine the study group which consisted of 593 university students from Damascus University, Syria. Findings and Results: According to canonical correlation analysis mindfulness was the most important among the positive factors set, while over-identified was the most important among the negative factors set. On the other hand, common variance of common-humanity and self-kindness was quite large, indicating multicollinearity between these two factors. Additionally, the contribution of common humanity was negligibly small; therefore, it can be excluded from the model with a small sacrifice in explained variance. Conclusions and Recommendations: Although the results of this study suggest the exclusion the common-humanity factor from the self-compassion structure, more research should be conducted to support this finding both theoretically and empirically. Also, additional statistical methods should be used to explore the complex relationship between factors of self-compassion within different samples. (C) 2017 Ani Publishing Ltd. All rights reserved
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    Investigating The Effect of Exposure-Control Strategies on Item Selection Methods in MCAT
    (Assoc Measurement & Evaluation Education & Psychology, 2018) Mao, Xiuzhen; Ozdemir, Burhanettin; Wang, Yating; Xin, Tao
    This study aims to investigate the effect of different item exposure controlling strategies on item selection methods in the context of multidimensional computerized adaptive testing (MCAT). Additionally, this study aims to examine to what extend the restrictive threshold (RT) and the restrictive progressive (RPG) exposure methods suppress the item exposure rates and increase the exposure rates of underexposed items without losing psychometric precision in MCAT. For this purpose, the performance of four item selection methods with and without exposure controls are evaluated and compared so as to determine how results differ when item exposure controlling strategies are applied with Monte-Carlo simulation method. The four item selection methods employed in this study are D-optimality, Kullback-Leibler information (KLP), the minimized error variance of linear combination score with equal weight (V1), the composite score with optimized weight (V2). On the other hand, the maximum priority index (MPI) method proposed for unidimensional CAT and two other item exposure control methods, that are RT and RPG methods proposed for cognitive diagnostic CAT, are adopted. The results show that: (1) KLP, D-optimality, and V1 performed better in recovering domain scores, and all outperformed V2 with respect to precision; (2) although V1 and V2 offer improved item bank usage rates, KLP, D-optimality, V1, and V2 produced an unbalanced distribution of item exposure rates; (3) all exposure control strategies improved the exposure uniformity greatly and with very little loss in psychometric precision; (4) RPG and MPI performed similarly in exposure control, and outperformed RT exposure control method.
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    Prevalence of Nomophobia among University Students: A Comparative Study of Pakistani and Turkish Undergraduate Students
    (Modestum Ltd, 2018) Ozdemir, Burhanettin; Cakir, Ozlem; Hussain, Irshad
    This study focused on to examine prevalence of nomophobia among university students; and the relationship among nomophobia, self-esteem, loneliness and self happiness with respect to gender and year of study of the university students in Pakistan and Turkey. The study subjects consisted of 729 students 368 (50.5%) of which were from Turkey and 361 (49.5%) from Pakistan. The data were collected by using Nomophobia Scale (NMP-Q), UCLA Loneliness Scale (ULS-8), Self-Happiness Scale, and Rosenberg' Self-Esteem Scale by the researchers from Pakistan and Turkey respectively. The relationship and the effect of each psychological structure on nomophobia were examined with multiple linear regression model. The difference across the categories of independent variables on each of the dependent variables (loneliness, self happiness, self-esteem and nomophobia) and on linear combination of dependent variables for each country was examined by multivariate MANOVA. According to multivariate effects results, the main effect of gender on self-esteem and nomophobia was statistically significant which indicates that differences between male and female students with respect to self-esteem and nomophobia were significant. The study demonstrated differences between Turkish and Pakistani students' score on nomophobia, loneliness and self-happiness were significant, while difference on self-esteem across countries was not statistically significant.