Papers by Vesna Luzar-Stiffler
Journal of Computing and Information Technology, 2008
The goal of this paper is to demonstrate the analytical use of a statistical tool ANOM (more comm... more The goal of this paper is to demonstrate the analytical use of a statistical tool ANOM (more commonly used by quality control engineers), mixed model analysis and other statistical tools (used in social sciences) to investigate differences found in Croatian high school student performance in mathematics examinations, recently developed as part of the National Assessment project.
Journal of Computing and Information Technology, 2002
The purpose of the article is to demonstrate an equivalence testing software application written ... more The purpose of the article is to demonstrate an equivalence testing software application written under SAS 1 Institute software designed for use by pharmaceutical and other medical research professionals. Besides making the entire equivalence testing procedure easier and more efficient, the application "EquivEasy" offers three main advantages over similar software: a) testing for 3 3 in addition to 2 2 crossover designs, b) familiar SAS user environment, and c) export flexibility (MS Word, PDF, HTML). Two case studies are presented with report results provided in tabular and graphical form.
Efficacy of Calcipotriol-Betamethasone Ointment in Patients with Mild to Moderate Plaque Psoriasis: Subgroup Analyses
Dermatology, 2019
Background: Several factors have been shown to affect psoriasis pathogenesis, clinical presentati... more Background: Several factors have been shown to affect psoriasis pathogenesis, clinical presentation and treatment response. Objectives: The aim of this study was to investigate the potential relationship between patients’ baseline characteristics and the efficacy of calcipotriol-betamethasone ointment in patients with mild to moderate plaque psoriasis and to evaluate whether the efficacy is consistent across subgroups. Method: Using data from the therapeutic equivalence study on patients with plaque psoriasis, post hoc analyses were performed to evaluate the impact of baseline demographic and disease characteristics, habits and comorbidities on the response to treatment with calcipotriol-betamethasone ointment. Results: Body mass index (BMI) and obesity were each independently associated (univariate analysis, p < 0.05) with reduction in modified Psoriasis Area and Severity Index (mPASI) and PASI75 (≥75% improvement in mPASI from baseline). Increased body weight is more common in patients with late-onset psoriasis. There was a significant trend for lower response rates with increasing BMI (p = 0.007) and obesity (p = 0.003). The odds of achieving PASI75 is 2.3 times lower for obese compared to normal-weight subjects.If patients with obesity or hypertension were treated with calcipotriol-betamethasone, they were still more likely to achieve PASI75 after 4-week treatment compared to vehicle (p < 0.001). Conclusion: Increased BMI and obesity present risk factors for reduced treatment effectiveness. Importantly, the efficacy of calcipotriol-betamethasone ointment was consistent in all subgroups.
The aim of this paper is to demonstrate the analytical use of a statistical tool (ANOM), more com... more The aim of this paper is to demonstrate the analytical use of a statistical tool (ANOM), more commonly used by quality control engineers, to investigate differences found in Croatian high school student performance on the Mathematics exam, recently developed as a part of the National Examinations Project
Proceedings of the ITI 2009 31st International Conference on Information Technology Interfaces
Effects of urban ozone pollution on hospitalizations for exacerbation of chronic obstructive pulmonary disease
Background: There are epidemiological data of adverse outcomes for COPD from urban ozone and rela... more Background: There are epidemiological data of adverse outcomes for COPD from urban ozone and related photochemical oxidants, but their relationship may be complex. The aim of this study was to investigate the associations between O3 and NO2 and daily COPD hospitalizations, adjusting for acute respiratory infections, weather and seasonality. Methods: Daily hospitalizations for COPD were regressed on pollutants and potential confounding variables using an autoregressive Poisson model. The relative risks of COPD hospitalization were calculated for the 25th to 75th percentile and 95th to 99th percentile increase in each of the selected pollutant concentrations. Results: The risk for COPD hospitalizations was significant both for 25th to 75th percentile and 95th to 99th percentile increase in concentrations of NO2 (RR=1.09; 95% CI: 1.02, 1,17 and RR=1,12; 95% CI: 1.03, 1.22, respectively) and O3 (RR=1.19; 95% CI: 1.05, 1.35 and RR=1.09; 95% CI: 1.03, 1,17). At the lower percentile change in ambient levels, the risk for ozone paradoxically increased whereas for NO2 decreased. A comparison among the standardized regression coefficients indicates that the most important risk for COPD hospitalizations was associated with ozone. Conclusion: The current results indicate the most important risk for COPD exacerbations to be associated with ozone supporting reduction in ambient ozone levels. However, in urban area the improvement in health outcomes for ozone cannot be completely achieved by reducing NO emissions although benefit may be expected in suburban areas.
Journal of Computing and Information Technology, 2004
The motivation for this research stemmed from a desire to create visual aids to help researchers/... more The motivation for this research stemmed from a desire to create visual aids to help researchers/managers interpret ensembles of decision tree outputs generated by various algorithms. The method employed a simulation experiment (using only bagging) followed by application of the new visualization tools on actual survey data. Simulated data, with a pre-specified structure, were "bagged" with the results presented using five graphical tools that recreated (and/or portrayed) the known data structures captured by the bagging algorithm. Then the same methodology was generalized to a structurally unknown, virgin (survey) data set. Results of the research are that five visual aids tools were examined (two of which are new approaches) and found to be useful for making action-oriented interpretations from e.g., web-survey data.
Aaps Pharmscitech, 2019
The aim of this work is to evaluate average bioequivalence (ABE) and population bioequivalence (P... more The aim of this work is to evaluate average bioequivalence (ABE) and population bioequivalence (PBE) statistical approaches so as to identify which approach is most suitable for in vitro bioequivalence (IVBE) testing of nasal spray products. For droplet size distribution (DSD) and spray pattern (SP), in vitro data were collected using a wellestablished nasal spray on the market (Nasonex®, manufactured by Merck Sharp & Dohme Limited). Simulations were performed using in vitro data to comparatively investigate ABE and PBE tests. For highly variable parameters such as SP area, this study clearly demonstrates that the level of agreement between ABE and PBE test conclusions is much smaller as compared with that of DSD Dv(50), which was found to have moderate variability. PBE approach dictates equivalence for both means and variances, and was found to handle both SP and DSD parameters with similar passing rates compared to the passing rates from the ABE approach. However, pronounced asymmetric behavior of PBE empirical power curves for highly variable SP area was observed. A modified PBE statistical approach is proposed for DSD span and Dv(50) in vitro parameters, where acceptance criteria would be based on comparison of reference/branded product to itself as part of Bpre-IVBE study^via innovative statistical bootstrap simulations. Due to inherent high variability of the SP area parameter driving pronounced asymmetric behavior of PBE power curves, and due to unclear in vivo relevance for SP area and ovality, authors propose that SP parameters be used as development and quality control tools rather than for demonstration of IVBE.
The aim of this poster is to show how the results of a National assessment were exhibited to the ... more The aim of this poster is to show how the results of a National assessment were exhibited to the schools through a simple, clear, and easily interpreted report created using SAS reporting and ODS thus minimizing potentially misleading statistical interpretations of results.
Periodicum Biologorum, 2010
Aim: The presented study reports a quantitative gait analysis and different adaptive strategies e... more Aim: The presented study reports a quantitative gait analysis and different adaptive strategies evaluation on 12 male adults, war trauma transtibial (TT) amputees, fitted with prostheses. Methods: Gait analysis included kinematics (joint mobility variables) prosthetic and healthy legs in 12 TT amputees and 12 able-bodied persons/individuals. Results: The results disclose asymmetry in gait parameters between the amputated and sound legs, as well as between transtibial amputees and able-bodied persons. Kinematic results of the amputees and a control group, showed significantly reduced prosthetic maximum ankle plantar flexion (p<0.01), decreased hip adduction (p< 0.05) and increased knee flexion at stance phase (p< 0.1) for the left, healthy legs of amputees. Conclusion: Although adult traumatic TT amputees have great potential for enhancement of function through appropriate rehabilitation and use of effective prosthetic devices, they adapt a unique way of ambulating with the ...
Effects of urban ozone pollution on hospitalizations for exacerbation of chronic obstructive pulmonary disease
European Respiratory Journal, 2015
Background: There are epidemiological data of adverse outcomes for COPD from urban ozone and rela... more Background: There are epidemiological data of adverse outcomes for COPD from urban ozone and related photochemical oxidants, but their relationship may be complex. The aim of this study was to investigate the associations between O3 and NO2 and daily COPD hospitalizations, adjusting for acute respiratory infections, weather and seasonality. Methods: Daily hospitalizations for COPD were regressed on pollutants and potential confounding variables using an autoregressive Poisson model. The relative risks of COPD hospitalization were calculated for the 25th to 75th percentile and 95th to 99th percentile increase in each of the selected pollutant concentrations. Results: The risk for COPD hospitalizations was significant both for 25th to 75th percentile and 95th to 99th percentile increase in concentrations of NO2 (RR=1.09; 95% CI: 1.02, 1,17 and RR=1,12; 95% CI: 1.03, 1.22, respectively) and O3 (RR=1.19; 95% CI: 1.05, 1.35 and RR=1.09; 95% CI: 1.03, 1,17). At the lower percentile change in ambient levels, the risk for ozone paradoxically increased whereas for NO2 decreased. A comparison among the standardized regression coefficients indicates that the most important risk for COPD hospitalizations was associated with ozone. Conclusion: The current results indicate the most important risk for COPD exacerbations to be associated with ozone supporting reduction in ambient ozone levels. However, in urban area the improvement in health outcomes for ozone cannot be completely achieved by reducing NO emissions although benefit may be expected in suburban areas.
ITI 2008 - 30th International Conference on Information Technology Interfaces, 2008
The aim of this paper is to demonstrate the analytical use of a statistical tool (ANOM), more com... more The aim of this paper is to demonstrate the analytical use of a statistical tool (ANOM), more commonly used by quality control engineers, to investigate differences found in Croatian high school student performance on the Mathematics exam, recently developed as a part of the National Examinations Project
Konstantin Momirovic (1932–2004) memorial session Data mining, statistics and biometrics
ITI 2008 - 30th International Conference on Information Technology Interfaces, 2008
Proceedings of the ITI 2008 30<sup>th</sup> International Conference on Information Technology Interfaces
ITI 2008 - 30th International Conference on Information Technology Interfaces, 2008
27th International Conference on Information Technology Interfaces, 2005.
The purpose of this article is to introduce a new procedure for detecting subject outlier(s) in d... more The purpose of this article is to introduce a new procedure for detecting subject outlier(s) in data from a fully replicated crossover design. The suggested procedure is an adjustment to a test based on the order statistics of the twosample Hotelling T 2 , introduced by Liu and Weng. Results from an empirical power study indicate that the proposed procedure is, on average, as powerful as, for example, the equivalent procedure for detecting outliers in data from a standard crossover design.
Knowledge and use of folic acid in Croatian pregnant women—a need for health care education initiative
Reproductive Toxicology, 2006
Adequate periconceptional folic acid (FA) intake reduces the risk of neural tube defects. There a... more Adequate periconceptional folic acid (FA) intake reduces the risk of neural tube defects. There are still no official FA supplementation guidelines, FA fortification policies or larger studies of awareness regarding FA or number of planned pregnancies in Croatia. This study assesses the knowledge and practice regarding FA supplementation and reports the trends in pregnancy planning in Croatia. A total of 569 pregnant women completed an anonymous questionnaire and about 72% of them were aware of the benefits of FA. Despite 75.53% of planned pregnancies, only 14.41% of all women took FA appropriately. Croatian women get information about FA from the media, health professionals and friends, but 63.77% got this information too late. The present study showed low percentage of appropriate FA intake despite high number of planned pregnancies in Croatia. It emphasizes the need for immediate and continuous public health education initiative about FA intake targeted to the women of childbearing age before their pregnancies have occurred.
Journal of Computing and Information Technology, 2001
A sample of 7000+ students was analyzed by the University Computing Centre (SRCE) staff to evalua... more A sample of 7000+ students was analyzed by the University Computing Centre (SRCE) staff to evaluate course satisfaction, teacher performance, and changing course demands. Findings indicated adequate overall performance, and changing course content needs over a four year time period. The major conclusion of the Project (SOCRATES) is that the software product developed during the research can become an economical and useful tool in helping to shape administrator efforts and decisions regarding the allocation of scarce organizational resources and in the development of new course offers at SRCE.
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Papers by Vesna Luzar-Stiffler