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The Kumaraswamy distribution is doubly limited, continuous, very flexible, and is widely applied in hydrology and related areas. Recently, several families of distributions based on this distribution have emerged. To make a contribution regarding some asymptotic aspects related to the inferential analysis, we derived an analytic expression of order n − 1 / 2 , where n is the sample size, for the skewness coefficient of the distribution of the maximum likelihood estimators of the parameters of the Kumaraswamy distribution. A simulation study and an application are presented to illustrate that, when the sample size is small, the likelihood inferences may not be reliable. We also obtain Bartlett correction factors for the likelihood ratio statistic as well as the results of the bootstrap likelihood ratio test and bootstrap Bartlett correction and present a Monte Carlo simulation study to compare the rejection rates of the tests in question. [ABSTRACT FROM AUTHOR]

Beta regression models have been widely used to model rates and proportions. We obtain a matrix formula of order where n is the sample size, for the skewness coefficient of the distribution of the maximum likelihood estimators of the linear parameters in varying dispersion beta regression models. The formula can be used to verify whether inference based on the asymptotic distribution of the maximum likelihood estimators should be performed. A simulation study and two applications are presented to illustrate the results. [ABSTRACT FROM AUTHOR]

Background: Laparoscopic surgery for rectal cancer is associated with improved postoperative outcomes compared to open surgery; however, economic studies have yielded contradictory results. The aim of this study was to compare the clinical and economic outcomes of laparoscopic versus open surgery for patients with rectal cancer., Methods: Propensity score matching analysis was performed in a retrospective cohort of patients who underwent elective low anterior resection for rectal cancer treatment by laparoscopic and open surgery in a single Brazilian cancer center. Matched covariates included age, gender, body mass index, pTNM stage, American Society of Anesthesiologists score, type of anesthesia, neoadjuvant chemoradiotherapy, and interval between neoadjuvant chemoradiotherapy and index surgery. The clinical and economic outcomes were evaluated. The follow-up period was within 30 days of the index procedure. The clinical outcomes were reoperation, postoperative complications, operative time, length of stay in the intensive care unit, and postoperative hospital stay. For economic outcomes, a cost analysis was used to compare the costs., Results: Initially, 220 patients were evaluated. After propensity score matching, 100 patients were included in the analysis (50 patients in the open surgery group and 50 patients in the laparoscopic surgery group). There were no differences in patients' baseline characteristics. Operative time was longer for laparoscopic surgery (247 minutes vs 285 minutes, P =0.006). There were no significant differences in other clinical outcomes. The hospital costs were similar between the two groups (Brazilian reais 21,233.15 vs Brazilian reais 21,529.28, P =0.115), although the intraoperative costs were higher for laparoscopic surgery, mainly owing to the surgical devices and the theater-related costs. The postoperative costs were lower for laparoscopic surgery, owing to lower intensive care unit, ward, and reoperation costs., Conclusion: Laparoscopic surgery for rectal cancer is not costlier than open surgery from the health care provider's perspective, since the intraoperative costs were offset by lower postoperative costs. Open surgery tends to have a longer length of stay., Competing Interests: Disclosure All authors have completed the ICMJE form for disclosure of potential conflicts of interest. Daiane Oliveira Tayar reports personal fees from Johnson & Johnson Medical Brazil, outside the submitted work. This study was conducted without any external influence. The authors report no other conflicts of interest in this work.