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Publication Date: 2025
Journal of Isfahan Medical School (10277595) 43(832)pp. 1173-1181
Background: This study aimed to determine the relationship between COVID-19 infection and chronic fatigue syndrome. Methods: A cross-sectional, descriptive-analytical study was conducted on individuals aged 18 to 60 without underlying medical conditions who had contracted COVID-19 within the past 6 to 12 months and had visited selected COVID-19 centers in Isfahan for outpatient PCR testing. Inclusion criteria were PCR-confirmed infection and participant consent, while those with a history of hospitalization or physical/mental comorbidities were excluded. A sample of 386 participants was randomly selected from a list of 2,863 in the comprehensive COVID19 database. Fatigue was assessed using the Chalder Fatigue Questionnaire, which had a Cronbach's alpha of 0.91, validated by Fallah and Taghizadeh in Iran. Findings: The average fatigue score among patients was 29.72 (ranging from 14 to 70), which is lower than the midpoint threshold of 42. There was no significant difference in fatigue levels between males and females, nor in average fatigue levels with age and BMI. However, with increasing age, the mean fatigue score decreased slightly. The mean fatigue score for individuals with a normal BMI was slightly lower than for those with an abnormal BMI. Fatigue levels were higher in less active occupations such as students, retirees, and homemakers compared to hospital staff, office workers, and laborers. Conclusion: The results suggest that chronic fatigue levels 6 to 12 months post-COVID-19 infection in individuals who had outpatient PCR testing are generally low or very low. © 2025, Isfahan University of Medical Sciences(IUMS). All rights reserved.
Publication Date: 2024
Journal of Health System Research (27834093) 20(3)pp. 295-304
Background: In this research, the researcher aims to model the adherence of patients with coronary heart disease (CHD) based on coping strategies and disease perception with the mediation of self-efficacy and psychological distress. Methods: This cross-sectional study was conducted on patients with CHD. The statistical population included patients with CHD in Isfahan Province, Iran, with the sample consisting of patients referred to Shahid Chamran Hospital in Isfahan City which were selected using purposeful sampling method. Data collection was done through the Adherence in Chronic Diseases Scale (ACDS), the Billings and Moss Coping Strategies Questionnaire, the Lovibond and Lovibond Psychological Distress Questionnaire, and the Cardiovascular Management Self-Efficacy Questionnaire developed by Steca et al. Comparative tests, correlation analysis methods, and structural equation modeling (SEM) were used to investigate the relationships between different factors. Findings: Coping strategies affected the adherence to treatment of patients with CHD, both directly and through the mediation of self-efficacy and psychological distress. The SEM method was used to test the mentioned model. The results of the analysis indicated that all the fit indices obtained from the analysis supported the fit of SEM with the compiled data [χ2 (degree of freedom or df = 94) = 157.54, χ2/df = 168, comparative fit index (CFI) = 0.959, goodness of fit index (GFI) = 0.915, adjusted GFI (AGFI) = 0.877, and root mean square error of approximation (RMSEA) = 0.056]. Conclusion: It can be concluded that coping strategies have a causal effect on adherence to treatment in patients with CHD with the mediating role of psychological distress and self-efficacy. The model has a good fit. © 2024, Isfahan University of Medical Sciences(IUMS). All rights reserved.
Publication Date: 2024
Journal of Clinical Medicine (20770383) 13(22)
Background: Aseptic nonunion of femoral shafts after intramedullary nailing (IMN) can be a challenging condition that may lead to long-term disability and the need for multiple surgical procedures. This study compared the clinical and radiological outcomes between exchange nailing and augmentative plating with bone grafting. Methods: In this multicenter, prospective, single-blind, randomized controlled trial, patients with aseptic nonunion of the femoral shaft after IMN were randomly assigned to receive exchange nailing or augmentative plating. The primary outcomes measured were the time to bone union and union rate 12 months after revision surgery. The secondary outcomes included operative time, blood loss, hospitalization duration, pain level using the visual analog scale (VAS), knee range of motion (ROM), and complication rates. Results: The augmentative plating group had a significantly shorter mean time to union (5.39 ± 1.29 months) compared with the exchange nailing group (7.38 ± 1.97 months; p < 0.001). The union rates at 12 months were 100% in the augmentative plating group and 89.65% in the exchange nail group. Augmentative plating resulted in a shorter operation time (99.46 ± 11.08 min vs. 106.45 ± 12.22 min; p = 0.025) and reduced blood loss (514.79 ± 45.87 mL vs. 547.72 ± 54.35 mL; p = 0.016). Significant pain reduction was observed in the augmentative plating group, with preoperative VAS scores decreasing from 6.04 ± 2.28 to 2.64 ± 1.50, compared with a decrease from 5.66 ± 2.21 to 3.66 ± 2.19 in the exchange nailing group (p = 0.047). Knee ROM improved significantly in the augmentative plating group (p = 0.0176). The complication rate was lower in the augmentative plating group (3.57%) than in the exchange nail group (17.24%). Conclusions: Augmentative plating with autologous bone grafting is superior to exchange nailing for treating aseptic nonunion of femoral shafts. It is associated with faster healing, higher union rates, better clinical and functional outcomes, and fewer complications. We recommend this technique as the preferred treatment option for such complex cases. © 2024 by the authors.
Publication Date: 2021
Statistical Papers (09325026) 62(5)pp. 2453-2471
It has been shown in the literature that judgment post stratification (JPS) sampling design often leads to more efficient statistical inference than what is possible to obtain in simple random sampling (SRS) design of comparable size. Since the JPS is a cost-efficient sampling design, a large enough sample size may not be available to use normal theory of the estimators. In this paper, we describe two bootstrap methods for JPS sampling scheme, one of which has been already used in the literature without studying its consistency and the other is new. We also show that both bootstrap approaches are consistent. We then investigate the use of the bootstrap methods for constructing confidence intervals for the population mean and compare them with the confidence interval of the population mean obtained via normal approximation (NA) method using Monte Carlo simulation. It is found that for the asymmetric distributions, one of the bootstrap methods we describe in the paper often leads to a closer coverage probability (CP) to the nominal level than NA method. Finally, a real dataset is analysed for illustration. © 2020, Springer-Verlag GmbH Germany, part of Springer Nature.
Publication Date: 2021
Brazilian Journal of Probability and Statistics (01030752) 35(2)pp. 375-391
This work deals with problem of estimating the odds using judgment post stratification (JPS) sampling design. Several estimators of the odds are described and the asymptotic normality of each of them is established. Monte Carlo simulation study is then used to compare different estimators of the odds in the JPS with the standard estimator in simple random sampling (SRS) with replacement for both perfect/imperfect ranking and for both JPS data with/without empty strata. The comparison results indicate that the estimators developed here can be highly more efficient than their SRS counterpart in some certain circumstances. Finally, a real dataset from the third National Health and Nutrition Examination Survey (NHANES III) is employed for illustration purposes. © Brazilian Statistical Association, 2021.
Publication Date: 2018
Journal of Modern Applied Statistical Methods (15389472) 17(1)
Most control charts require the assumption of normal distribution for observations. When distribution is not normal, one can use non-parametric control charts such as sign control chart. A deficiency of such control charts could be the loss of information due to replacing an observation with its sign or rank. Furthermore, because the chart statistics of T2 are correlated, the T2 chart is not a desire performance. Non-parametric bootstrap algorithm could help to calculate control chart parameters using the original observations while no assumption regarding the distribution is needed. In this paper, first, a bootstrap multivariate control chart is presented based on Hotelling's T2 statistic then the performance of the bootstrap multivariate control chart is compared to a Hotelling's T2 parametric multivariate control chart, a multivariate sign control chart, and a multivariate Wilcoxon control chart using a simulation study. Ultimately, the bootstrap multivariate control chart is used in an empirical example to study the process of sugar production. © 2018 JMASM, Inc.
Publication Date: 2018
Journal of Modern Applied Statistical Methods (15389472) 17(1)pp. 1-27
Most control charts require the assumption of normal distribution for observations. When distribution is not normal, one can use non-parametric control charts such as sign control chart. A deficiency of such control charts could be the loss of information due to replacing an observation with its sign or rank. Furthermore, because the chart statistics of T2 are correlated, the T2 chart is not a desire performance. Non-parametric bootstrap algorithm could help to calculate control chart parameters using the original observations while no assumption regarding the distribution is needed. In this paper, first, a bootstrap multivariate control chart is presented based on Hotelling’s T2 statistic then the performance of the bootstrap multivariate control chart is compared to a Hotelling’s T2 parametric multivariate control chart, a multivariate sign control chart, and a multivariate Wilcoxon control chart using a simulation study. Ultimately, the bootstrap multivariate control chart is used in an empirical example to study the process of sugar production. © 2018 JMASM, Inc.
Publication Date: 2017
Applied Stochastic Models in Business and Industry (15264025) 33(6)pp. 694-716
Various charts such as |S|, W, and G are used for monitoring process dispersion. Most of these charts are based on the normality assumption, while exact distribution of the control statistic is unknown, and thus limiting distribution of control statistic is employed which is applicable for large sample sizes. In practice, the normality assumption of distribution might be violated, while it is not always possible to collect large sample size. Furthermore, to use control charts in practice, the in-control state usually has to be estimated. Such estimation has a negative effect on the performance of control chart. Non-parametric bootstrap control charts can be considered as an alternative when the distribution is unknown or a collection of large sample size is not possible or the process parameters are estimated from a Phase I data set. In this paper, non-parametric bootstrap multivariate control charts |S|, W, and G are introduced, and their performances are compared against Shewhart-type control charts. The proposed method is based on bootstrapping the data used for estimating the in-control state. Simulation results show satisfactory performance for the bootstrap control charts. Ultimately, the proposed control charts are applied to a real case study. Copyright © 2017 John Wiley & Sons, Ltd.
Publication Date: 2011
Computational Statistics and Data Analysis (01679473) 55(1)pp. 578-587
Efron (1979) introduced the bootstrap method for independent data but it cannot be easily applied to spatial data because of their dependency. For spatial data that are correlated in terms of their locations in the underlying space the moving block bootstrap method is usually used to estimate the precision measures of the estimators. The precision of the moving block bootstrap estimators is related to the block size which is difficult to select. In the moving block bootstrap method also the variance estimator is underestimated. In this paper, first the semi-parametric bootstrap is used to estimate the precision measures of estimators in spatial data analysis. In the semi-parametric bootstrap method, we use the estimation of the spatial correlation structure. Then, we compare the semi-parametric bootstrap with a moving block bootstrap for variance estimation of estimators in a simulation study. Finally, we use the semi-parametric bootstrap to analyze the coal-ash data. © 2010 Elsevier B.V. All rights reserved.
Publication Date: 2011
Procedia Environmental Sciences (18780296) 3pp. 81-86
In the spatial statistics it is often assumed that the data follow a Gaussian random field. Efron introduced bootstrap method for independent data analysis (IIDB) but it can not be applied in spatial data analysis because of dependency of observations. In this paper, an algorithm is given for spatial semi-parametric bootstrap (SSPB) method to estimate the precision measures of plug-in kriging predictor of random field. We also compare IIDB and SSPB methods for analysis of plug-in kriging predictor in a Monte-Carlo simulation study. Finally, we use SSPB method for analysis of finite strain data in geology. © 2010 Published by Elsevier Ltd. Ltd.
Publication Date: 2010
Iranian Journal of Environmental Health Science and Engineering (17352746) 7(1)pp. 71-80
The purpose of this study was to undertake a spatial analysis of total organic carbon, electrical conductivity and nitrate, in order to produce a pollution dispersion and prediction map for the investigated area in the province of Isfahan in Iran. The groundwater samples were collected from a zone as a pilot study area of 80 km2, including 25 water wells, based on the criteria of vulnerability assessment projects, that is, about one well per 3 km2, during four seasons in 2008-09. In order to make any inferences about the areas that did not have well data, a statistical relationship between explanatory total organic carbon, electrical conductivity and nitrate variables related to well coordination was developed. The probability of the presence of elevated levels of the three compounds in the groundwater was predicted using the best-fit variogram model. According to spatial analysis, the highest R2=0.789 achieved was related to electrical conductivity and followed the exponential model with 0.266 for NO3- (spherical model) and 0.322 for total organic carbon (exponential model) in the spring 2009. This showed the high confidence level for electrical conductivity dataset and forecasted trends. The results of the spatial analysis demonstrated that the transfer trends of electrical conductivity in the groundwater resources followed the route of groundwater movement in all seasons. However, for nitrate and total organic carbon, a definite trend was not obtained and pollution dispersion depended on many parameters.
Publication Date: 2009
Computers and Geosciences (00983004) 35(3)pp. 626-634
In this paper, the finite strain data (FSD) collected from a Sheeprock thrust sheet in Utah are spatially analyzed. The steps and special manner of spatial analysis of these data are examined due to the importance and influence of data characteristics on spatial prediction accuracy. To do so, the exponential and spherical parametric variogram models with and without nugget effects are fitted by maximum likelihood and restricted maximum likelihood methods on original and normally transformed data. We also fitted other models to classical and robust empirical variograms by ordinary least squares and weighted least squares methods. Next, these models are applied on data and edited data by using robust kriging. Finally, the accuracy of the obtained results are compared with Mukul's model by cross-validation in order to choose the best variogram model for FSD and also specify the importance of attention to characteristics of the data in spatial data analysis. © 2008 Elsevier Ltd. All rights reserved.
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