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Māra Delesa-Vēliņa
Laboratory for Statistical Analysis and Research, Faculty of Physics, Mathematics and Optometry, University of Latvia, Riga, Latvia

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Article
Published: 17 March 2021 in Lithuanian Mathematical Journal
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We develop a new robust empirical likelihood-based test for comparing the trimmed means of two independent populations. The simulation results indicate that the test has asymptotically correct level under various data distributions and controls the Type I error adequately for medium-size samples. For nonnormal data distributions, the power of the test is comparable to robust alternatives like Yuen’s test for the trimmed means and considerably exceeds that of the tests based on the means. In small sample settings the test version for the difference of 10% trimmed means exhibits robustness to the combined presence of nonnormality and heterogeneity.

ACS Style

Māra Delesa-Vēliņa; Jānis Valeinis; George Luta. Comparing Two Independent Populations Using a Test Based on Empirical Likelihood and Trimmed Means. Lithuanian Mathematical Journal 2021, 61, 199 -216.

AMA Style

Māra Delesa-Vēliņa, Jānis Valeinis, George Luta. Comparing Two Independent Populations Using a Test Based on Empirical Likelihood and Trimmed Means. Lithuanian Mathematical Journal. 2021; 61 (2):199-216.

Chicago/Turabian Style

Māra Delesa-Vēliņa; Jānis Valeinis; George Luta. 2021. "Comparing Two Independent Populations Using a Test Based on Empirical Likelihood and Trimmed Means." Lithuanian Mathematical Journal 61, no. 2: 199-216.

Journal article
Published: 16 November 2019 in Applied Sciences
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The visual search performance of radiologists is systematically challenged due to the use of flat-panel displays when viewing multi-slice images. Three-dimensional visualization of information is expected to facilitate visual search for radiologists. However, as the differences in user performance, depending on radiologist experience, have not yet been assessed for real three-dimensional images, it is difficult to estimate the usability of new visualization systems for radiologists with different amounts of professional search experience. In this study, we aimed to determine how three-dimensional visual search is affected by radiologist experience and the physical properties of stimuli. Radiologists, residents, and medical students accomplished visual search tasks with varying set sizes and target-distractor similarities. Search items were presented on multiple display planes and image manipulation was conducted using a computer keyboard. We compared the search outcome and strategy among three groups of participants. All three groups submitted a similar number of correct responses depending on target-distractor similarity. However, in contrast to radiologists and residents, it took a considerably longer time for students to find the targets. The major differences were evident in search strategy when comparing the image manipulations of radiologists with those of residents and students. Our results demonstrated that experienced radiologists’ search performance benefited from seeing the entire three-dimensional view of an image, whereas residents and students focused instead on reducing the amount of information and searched in a selective manner. These findings should be taken into account when planning the implementation of new workstations with three-dimensional visualization in radiology.

ACS Style

Tatjana Pladere; Mara Delesa-Velina; Viktorija Andriksone; Reinis Pitura; Karola Panke; Gunta Krumina. Visual Search Performance and Strategy for Three-Dimensional Visualization Systems: Impact of Radiologist Experience. Applied Sciences 2019, 9, 4929 .

AMA Style

Tatjana Pladere, Mara Delesa-Velina, Viktorija Andriksone, Reinis Pitura, Karola Panke, Gunta Krumina. Visual Search Performance and Strategy for Three-Dimensional Visualization Systems: Impact of Radiologist Experience. Applied Sciences. 2019; 9 (22):4929.

Chicago/Turabian Style

Tatjana Pladere; Mara Delesa-Velina; Viktorija Andriksone; Reinis Pitura; Karola Panke; Gunta Krumina. 2019. "Visual Search Performance and Strategy for Three-Dimensional Visualization Systems: Impact of Radiologist Experience." Applied Sciences 9, no. 22: 4929.

Journal article
Published: 16 October 2019 in Photonics
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Volumetric display shows promising implications for healthcare related applications as an innovative technology that creates real three-dimensional (3D) image by illuminating points in three-dimensional space to generate volumetric images without image separation. We used eccentric photorefractometry to objectively study ocular performance in a practical environment by evaluating near work-induced refraction shift, accommodative microfluctuations, and pupil size for 38 young adults after viewing anaglyph, and volumetric 3D content for prolonged time. The results of our study demonstrate that participants who performed relative depth estimation task on volumetric 3D content were less likely to experience task-induced myopic refraction shift. For both 3D content types, we observed pupil constriction, that is possibly related to visual fatigue. For anaglyph 3D pupil constriction, onset was observed significantly sooner, compared to volumetric 3D. Overall, sustained work with 3D content, and small disparities or the fully eliminated possibility of accommodation-vergence conflict, not only minimizes near work-induced myopic shift, but also provide beneficial accommodation relaxation that was demonstrated in this study as hypermetropic shift for nearly half of participants.

ACS Style

Karola Panke; Tatjana Pladere; Mara Velina; Aiga Svede; Gunta Krumina. Objective User Visual Experience Evaluation When Working with Virtual Pixel-Based 3D System and Real Voxel-Based 3D System. Photonics 2019, 6, 106 .

AMA Style

Karola Panke, Tatjana Pladere, Mara Velina, Aiga Svede, Gunta Krumina. Objective User Visual Experience Evaluation When Working with Virtual Pixel-Based 3D System and Real Voxel-Based 3D System. Photonics. 2019; 6 (4):106.

Chicago/Turabian Style

Karola Panke; Tatjana Pladere; Mara Velina; Aiga Svede; Gunta Krumina. 2019. "Objective User Visual Experience Evaluation When Working with Virtual Pixel-Based 3D System and Real Voxel-Based 3D System." Photonics 6, no. 4: 106.

Original article
Published: 14 February 2019 in Journal of Statistical Theory and Practice
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We consider one of the classical problems in statistics: the inference for the two-sample location problem. In this paper, we present a new empirical likelihood (EL) method for the difference of two smoothed M-estimators. To deal with additional nuisance scale parameters, we use the plug-in empirical likelihood, and we establish asymptotic properties of the new estimators. For the empirical study, we consider the important case of the smoothed Huber M-estimator. Our empirical results show that the new method is a competitive alternative to the classical procedures regarding inference about the difference of two location parameters. The software implementation for the new empirical likelihood method is based on the R package EL, which has been developed for related two-sample problems.

ACS Style

Mara Velina; Janis Valeinis; George Luta. Empirical Likelihood-Based Inference for the Difference of Two Location Parameters Using Smoothed M-Estimators. Journal of Statistical Theory and Practice 2019, 13, 34 .

AMA Style

Mara Velina, Janis Valeinis, George Luta. Empirical Likelihood-Based Inference for the Difference of Two Location Parameters Using Smoothed M-Estimators. Journal of Statistical Theory and Practice. 2019; 13 (2):34.

Chicago/Turabian Style

Mara Velina; Janis Valeinis; George Luta. 2019. "Empirical Likelihood-Based Inference for the Difference of Two Location Parameters Using Smoothed M-Estimators." Journal of Statistical Theory and Practice 13, no. 2: 34.

Journal article
Published: 27 September 2016 in International Journal of Environmental Research and Public Health
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In this paper, we introduce an alternative to Yuen’s test for the comparison of several population trimmed means. This nonparametric ANOVA type test is based on the empirical likelihood (EL) approach and extends the results for one population trimmed mean from Qin and Tsao (2002). The results of our simulation study indicate that for skewed distributions, with and without variance heterogeneity, Yuen’s test performs better than the new EL ANOVA test for trimmed means with respect to control over the probability of a type I error. This finding is in contrast with our simulation results for the comparison of means, where the EL ANOVA test for means performs better than Welch’s heteroscedastic F test. The analysis of a real data example illustrates the use of Yuen’s test and the new EL ANOVA test for trimmed means for different trimming levels. Based on the results of our study, we recommend the use of Yuen’s test for situations involving the comparison of population trimmed means between groups of interest.

ACS Style

Mara Velina; Janis Valeinis; Luca Greco; George Luta. Empirical Likelihood-Based ANOVA for Trimmed Means. International Journal of Environmental Research and Public Health 2016, 13, 953 .

AMA Style

Mara Velina, Janis Valeinis, Luca Greco, George Luta. Empirical Likelihood-Based ANOVA for Trimmed Means. International Journal of Environmental Research and Public Health. 2016; 13 (10):953.

Chicago/Turabian Style

Mara Velina; Janis Valeinis; Luca Greco; George Luta. 2016. "Empirical Likelihood-Based ANOVA for Trimmed Means." International Journal of Environmental Research and Public Health 13, no. 10: 953.