Statistical Modelling with Birnbaum-Saunders Distribution

In this article, it is assumed that the distribution of the error terms is the Birnbaum-Saunders distribution in the process of one-way ANOVA. The Birnbaum-Saunders distribution has been widely used in reliability analysis especially in fatigue-life models. In reliability analysis, nonnormal distribution is much more common than the normal distribution. We obtain the estimation of the parameters og interest by maximum likelihood method. We also propose new test statistics based on these estimators . The efficiencies of the maximum likelihood estimators and the Type I errors obtained by using the proposed estimators are compared with normal theory via Monte Carlo simulation study. At the end of the study, the real life example is given just for the illustration of the method.

Impact of Shared Bus on Campus Travel and Space Optimization Based on Activity Travel Behavior

Based on the travel analysis of students in the Jiulonghu campus, this paper constructs a small-scale shared bus in the campus, explores the impact of shared traffic on campus travel, promotes the optimization design of campus space environment, and creates a more comfortable and convenient travel space. In order to overcome the shortcomings of the traditional trip-based research, this paper analyzes travel behavior from the perspective of activity-based travel concept framework, considering more activities and travel information. At the same time, in order to improve the richness of information, the explicit preference survey (RP) and the declarative preference survey (SP), which are added to the bus sharing customized travel platform, are used to collect data of personal attributes and travel diary. Firstly, based on the ArcGIS platform, this paper constructs the activity travel path generation tool, dynamic activity density distribution tool, and spatiotemporal path clustering tool and comprehensively analyzes the activity travel mode from the aspects of time distribution, spatial distribution, and category characteristics. Secondly, based on the travel activities, the location selection model (S-MNL) considering the heterogeneity of SP and RP data sources and the activity duration planning model (Cox regression), considering the nonnormal distribution of activity duration are established to analyze the impact of shared bus on students’ travel distance, travel time, and travel frequency. Finally, according to the analysis of modeling results, the impact of shared traffic on campus travel is analyzed, and the optimal design scheme of campus space is given. This paper uses the survey method based on declarative preference SP and the survey method based on explicit preference (RP) to get the actual and hypothetical travel response of travelers, which improves the data richness.

Impact of Selected Geriatric Syndromes on the Quality of Life in the Population Aged 60 and Older

Background: Geriatric syndromes represent a critical domain in the population more than 60 years old. Basic syndromes include frailty, sarcopenia, loss of body mass, and a mild cognitive disorder. These are significant problems which can affect the quality of life. In our study, the Rapid Geriatric Assessment (RGA) tool was used to assess the geriatric syndromes, and the WHOQOL-BREF was used to assess the quality of life to survey 498 respondents from a population aged 60 and older. In all the assessments, the distribution of variables was tested, a nonnormal distribution of variables was identified, and subsequently, nonparametric tests were performed to identify the differences between groups. The study showed that the domain of physical health and the psychological domain were most affected. The results have shown that individual geriatric syndromes affect certain domains of the quality of life of the population above 60 with various intensity.

Examining Nonnormal Latent Variable Distributions for Non-Ignorable Missing Data

Missing not at random (MNAR) modeling for non-ignorable missing responses usually assumes that the latent variable distribution is a bivariate normal distribution. Such an assumption is rarely verified and often employed as a standard in practice. Recent studies for “complete” item responses (i.e., no missing data) have shown that ignoring the nonnormal distribution of a unidimensional latent variable, especially skewed or bimodal, can yield biased estimates and misleading conclusion. However, dealing with the bivariate nonnormal latent variable distribution with present MNAR data has not been looked into. This article proposes to extend unidimensional empirical histogram and Davidian curve methods to simultaneously deal with nonnormal latent variable distribution and MNAR data. A simulation study is carried out to demonstrate the consequence of ignoring bivariate nonnormal distribution on parameter estimates, followed by an empirical analysis of “don’t know” item responses. The results presented in this article show that examining the assumption of bivariate nonnormal latent variable distribution should be considered as a routine for MNAR data to minimize the impact of nonnormality on parameter estimates.

Investigating the PROMIS Physical Function and Pain Interference Domains in Elite Athletes

Background: Multiple studies have demonstrated the National Institutes of Health (NIH) Patient-Reported Outcomes Measurement Information System (PROMIS) to be a responsive and efficient measure for patients undergoing orthopaedic surgery. While these studies were rigorous in their protocol and methodology, no efforts in recent literature have been made to identify if these reference scores apply to elite athletes. Purpose/Hypothesis: The purpose of this study was to determine whether there is a difference in the baseline scores of elite athletes versus the general population. We hypothesized that athletes’ PROMIS upper extremity general function (PROMIS-UE) and general physical function (PROMIS-PF) scores would vary substantially from the mean health state of the general population. We further hypothesized that these scores would be affected by specific sport and level of competition Study Design: Cross-sectional study; Level of evidence, 3. Methods: Three PROMIS computer adaptive test (CAT) domains were administered to elite athlete (≥18 years) volunteers (either in person or through email). An elite athlete was defined as one participating in sports at the collegiate level or higher. Test domains included PROMIS-PF, PROMIS-UE, and pain interference (PROMIS-PI). PROMIS domain t scores were defined and assessed against NIH reference values to identify significant differences. Distribution analysis was conducted using histograms and normality assessments. Domains were also subject to correlation analysis. Finally, subgroup analysis was conducted for all athlete characteristics to identify any factors associated with variance. Results: In total, 196 elite athletes (mean age, 21.1 years; range, 18.0-36.7 years) completed all 3 PROMIS-CAT forms. Overall, the mean scores were 56.0 ± 6.4, 58.1 ± 7.7, and 47.1 ± 7.3 for PROMIS-UE, PROMIS-PF, and PROMIS-PI, respectively. Distribution analysis showed nonnormal distribution for all 3 PROMIS domains (Kolmogorov-Smirnov test, P < .001). Similarly, in all 3 PROMIS domains the athletes displayed more disparate scores than the NIH-reported reference values (1-way sign test, P < .001). Only the presence of pain and sport played showed association with variance in PROMIS domain scores ( P < .001 and P = .003, respectively). Conclusion: Elite athletes displayed more disparate reference scores than the NIH-reported average of 50 for PROMIS-UE, PROMIS-PF, and PROMIS-PI. Furthermore, these forms were sensitive to varying levels of sport among collegiate athletes.

Difenoconazole Resistance Shift in Botrytis cinerea From Tomato in China Associated With Inducible Expression of CYP51

Gray mold caused by Botrytis cinerea is one of the most important diseases in tomato. It can be controlled effectively by demethylation inhibitor (DMI) fungicides, but their resistance status after long-term use in the field is unclear. The baseline sensitivity to difenoconazole of 142 B. cinerea isolates from China with no history of DMI usage was characterized, with a mean effective concentration for 50% mycelial growth inhibition (EC50) of 0.97 ± 0.50 μg/ml. EC50 values for difenoconazole sensitivity of another 248 isolates collected in 2011 and 2016 ranged from 0.04 to 11.99 μg/ml, and the frequency of difenoconazole sensitivity formed a nonnormal distribution curve. Detached fruit studies revealed that isolates with EC50 values of approximately 6.00 μg/ml were not controlled effectively. The mean EC50 of the resistant isolates changed from 6.74 to 8.65 μg/ml between 2011 and 2016. Positive cross-resistance was only observed between difenoconazole and two DMIs. One dual resistant isolate and one triple resistant isolate were found among the difenoconazole-resistant isolates collected in 2016, associated with point mutations in corresponding target proteins of the fungicides azoxystrobin and fludioxonil. This indicated that B. cinerea not only showed higher difenoconazole resistance levels but gradually changed from single to multiple fungicide resistance over time. No amino acid variation was found in the CYP51 protein. In the absence of difenoconazole, the relative expression of CYP51 was not significantly different in sensitive and resistant isolates. Induced expression of CYP51 is an important determinant of DMI resistance in B. cinerea from tomato. However, nucleotide variants found in the upstream region had no association with the fungicide resistance phenotype. These results will be helpful for the management of B. cinerea in the field.

MAD Control Chart for Autoregressive Models with Skew-Normal Distribution

The major problem in analyzing control charts is to work with autocorrelated data. This problem can be solved by fitting a suitable model to the data and using the control chart for the residuals. The problem becomes very important, when the distribution of observation is nonnormal, in addition to being autocorrelated. Much recent research has focused on the development of appropriate statistical process control techniques for the autocorrelated data or nonnormal distribution, but few studies have considered monitoring the process mean of both nonnormal and autocorrelated data. In this paper, a simulation study is conducted to compare the performances of the control chart based on the median absolute deviation method (MAD) with those of existing control charts for the skew normal distribution. Simulation results indicate considerable improvement over existing control charts for nonnormal data can be achieved when the control charts with control limits based on the MAD method are used to monitor the process mean of nonnormal autocorrelated data.

Systemic Factors Associated with Treatment Response in Diabetic Macular Edema

Purpose. To identify systemic factors that may influence the response to anti-VEGF therapy in patients with diabetic macular edema (DME). Methods. 35 patients undergoing anti-VEGF injections for centre-involving DME were studied in this prospective observational study. The primary outcome was change in macular thickness one month after treatment, measured using spectral-domain optical coherence tomography (OCT). At baseline, information on various systemic factors was collected including glycosylated hemoglobin (HbA1c), serum VEGF levels, lipid profile and markers of renal function, and blood pressure. Thirty-three of the 35 patients were included in this study. Nonparametric statistical tests were used for the analysis of the data in view of the nonnormal distribution of the outcome variables. Multivariate analysis was performed using logistic regression. Stata 12.1 software was used for the analysis. Main Outcome Measures. Reduction in macular central subfield thickness (on spectral-domain OCT) and change in logMAR visual acuity at one month after injection. Results. Lower HbA1c levels (7% or less) were significantly associated with greater reduction in central macular subfield thickness at one month after injection of bevacizumab or ranibizumab on both univariate analysis (p=0.012) and multivariate analysis (p=0.042). Conclusions. Better glycemic control is associated with a greater reduction in central macular thickness after the first injection of bevacizumab or ranibizumab in diabetic macular edema. Patients with high levels of HbA1c and poor response to anti-VEGF may benefit from strict control of their blood glucose.

A Randomized Placebo-Controlled N-of-1 Trial: The Effect of Proton Pump Inhibitor in the Management of Gastroesophageal Reflux Disease

Background. Gastroesophageal reflux disease (GERD) is the most frequent chronic gastrointestinal disorder. It is defined as a condition developed when the reflux of gastric contents causes troublesome symptoms (heartburn and regurgitation). This requires adequate treatment since it can lead to long-term complications including esophagus adenocarcinoma. Proton pump inhibitors (PPI) are generally used to treat GERD due to their high-security profile and efficiency on most patients. However, recurrent reflux despite initial treatment is frequent. N-of-1 trial is a study that allows the identification of the best treatment for each patient. The objective of this study is to compare the efficacy of standard dose with double dosage of esomeprazole, to improve the GERD symptoms in a single patient. Methods. A single-patient trial, placebo-controlled, randomized, double-blind, was carried out from September 25th, 2012, to April 26th, 2013. It included one outpatient at the gastroenterology service in a fourth-level hospital, diagnosed with nonerosive reflux disease (NERD). Yet, his symptoms were heartburn and reflux, and his endoscopic results were normal esophageal mucosa, without hiatal hernia, though pathological pH values. A no-obese male without any tobacco or alcohol usage received esomeprazole 40 mg/day and 40 mg/bid for 24 weeks. A standardized gastroesophageal reflux disease questionnaire (GerdQ) was used weekly to evaluate symptom frequency and severity. The consumption of 90% of the capsules was considered as an adequate treatment adherence. D’agostino–Pearson and Wilcoxon test were used to determine normal or nonnormal distribution and compare both treatments, respectively, both with a significant statistical difference of p<0.05. Results. The patient completed the study with 96% of adherence. The double dosage of esomeprazole did not improve the control of symptoms compared with the standard dosage. Mean symptomatic score was 9.5±0.5 and 10.2±0.6 for each treatment, respectively (p>0.05). Conclusion. There was no significant improvement in the patient GERD symptoms increasing the dose of oral esomeprazole during the 6 months of study. N-of-1 trials in chronic pathologies including GERD are recommended due to their potential value as systematic methods that evaluate therapies without strong scientific evidence.

Prospective Patient Reported Outcomes (PRO) Study Assessing Outcomes of Surgically Managed Ankle Fractures

Background: Ankle fractures are a common cause of morbidity that have increased in incidence over the past decade. The purpose of this study was to compare the outcomes and prognosis of various fracture subtypes by using 2 validated patient-reported outcome measures: the Patient-Reported Outcome Measurement Information System (PROMIS) Physical Function (PF) and Pain Interference (PI) Computer Adaptive Tests (CATs). Methods: Twelve-month postoperative PF and PI CATs were collected for 126 ankle fracture patients presenting between 2014 and 2017. Patients were stratified by ankle fracture subtype and refined by the presence/absence of concomitant deltoid injury or posterior malleolar fracture. Patients defined as members of vulnerable populations and patients presenting more than 2 weeks from time of injury or with prior acute ipsilateral fracture were excluded. The distribution of PF and PI T scores were assessed via a Shapiro-Wilk test and a 1-way analysis of variance. If significant differences were found between groups, pairwise comparisons were tested via Dwass, Steel, and Critchlow-Fligner multiple comparison analysis. Results: Mean values for the PROMIS PF and PI for each fracture subtype were calculated and compared to reference population mean (SD) T scores of 50 (10): isolated lateral malleolar (PF: 50/PI: 51), isolated medial malleolar (PF: 52/PI: 49), bimalleolar (PF: 48/PI: 50), trimalleoar (PF: 47/PI: 51), isolated posterior malleolar (PF: 53/PI: 44), and isolated syndesmotic injury (PF: 60/PI: 46). Shapiro-Wilk test indicated a nonnormal distribution for the postoperative PROMIS PF T scores across all fracture patients ( P = .0421). Conclusion: Operative fixation of an ankle fracture was able to return most patients to the population mean with regard to PROMIS function and pain regardless of fracture type. Level of Evidence: Level II, prospective comparative study.