Information criteria for nonlinear time series models

In this paper the performance of different information criteria for simultaneous model class and lag order selection is evaluated using simulation studies. We focus on the ability of the criteria to distinguish linear and nonlinear models. In the simulation studies, we consider three different versions of the commonly known criteria AIC, SIC and AICc. In addition, we also assess the performance of WIC and evaluate the impact of the error term variance estimator. Our results confirm the findings of different authors that AIC and AICc favor nonlinear over linear models, whereas weighted versions of WIC and all versions of SIC are able to successfully distinguish linear and nonlinear models. However, the discrimination between different nonlinear model classes is more difficult. Nevertheless, the lag order selection is reliable. In general, information criteria involving the unbiased error term variance estimator overfit less and should be preferred to using the usual ML estimator of the error term variance. © 2016 by De Gruyter

Perioperative morbidity of different operative approaches in early cervical carcinoma: a systematic review and meta-analysis comparing minimally invasive versus open radical hysterectomy

Purpose: Radical hysterectomy and pelvic lymphadenectomy is the standard treatment for early cervical cancer. Studies have shown superior oncological outcome for open versus minimal invasive surgery, but peri- and postoperative complication rates were shown vice versa. This meta-analysis evaluates the peri- and postoperative morbidities and complications of robotic and laparoscopic radical hysterectomy compared to open surgery. Methods: Embase and Ovid-Medline databases were systematically searched in June 2020 for studies comparing robotic, laparoscopic and open radical hysterectomy. There was no limitation in publication year. Inclusion criteria were set analogue to the LACC trial. Subgroup analyses were performed regarding the operative technique, the study design and the date of publication for the endpoints intra- and postoperative morbidity, estimated blood loss, hospital stay and operation time. Results: 27 studies fulfilled the inclusion criteria. Five prospective, randomized-control trials were included. Meta-analysis showed no significant difference between robotic radical hysterectomy (RH) and laparoscopic hysterectomy (LH) concerning intra- and perioperative complications. Operation time was longer in both RH (mean difference 44.79 min [95% CI 38.16; 51.42]), and LH (mean difference 20.96 min; [95% CI − 1.30; 43.22]) than in open hysterectomy (AH) but did not lead to a rise of intra- and postoperative complications. Intraoperative morbidity was lower in LH than in AH (RR 0.90 [0.80; 1.02]) as well as in RH compared to AH (0.54 [0.33; 0.88]). Intraoperative morbidity showed no difference between LH and RH (RR 1.29 [0.23; 7.29]). Postoperative morbidity was not different in any approach. Estimated blood loss was lower in both LH (mean difference − 114.34 [− 122.97; − 105.71]) and RH (mean difference − 287.14 [− 392.99; − 181.28]) compared to AH, respectively. Duration of hospital stay was shorter for LH (mean difference − 3.06 [− 3.28; − 2.83]) and RH (mean difference − 3.77 [− 5.10; − 2.44]) compared to AH. Conclusion: Minimally invasive radical hysterectomy appears to be associated with reduced intraoperative morbidity and blood loss and improved reconvalescence after surgery. Besides oncological and surgical factors these results should be considered when counseling patients for radical hysterectomy and underscore the need for new randomized trials. © 2021, The Author(s)

On robust local polynomial estimation with long-memory errors

Prediction in time series models with a trend requires reliable estimation of the trend function at the right end of the observed series. Local polynomial smoothing is a suitable tool because boundary corrections are included implicitly. However, outliers may lead to unreliable estimates, if least squares regression is used. In this paper, local polynomial smoothing based on M estimation is considered for the case where the error process exhibits long-range dependence. In constrast to the iid case, all M estimators are asymptotically equivalent to the least square solution, under the (ideal) Gaussian model. Outliers turn out to have a major eect on nonrobust bandwidth selection, in particular due to the change of the dependence structure. 1 Introduction 1.1 The model Let y 1 ; :::; y n be an observed time series such that y i = g(t i ) + i ; (1) where t i = i=n 2 [0; 1]; g(t) is an unknown suciently smooth function (e.g. in C 3 [0; 1]), i = G(Z i ) where Z i is a zero mean st..

An introduction to Markov Chains for interested high school students

SIGLEAvailable from TIB Hannover: RR 8460(2003,17) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Protective operative techniques in radical hysterectomy in early cervical carcinoma and their influence on disease-free and overall survival: a systematic review and meta-analysis of risk groups

Purpose!#!Radical hysterectomy with pelvic lymphadenectomy presents the standard treatment for early cervical cancer. Recently, studies have shown a superior oncological outcome for open versus minimal invasive surgery, however, the reasons remain to be speculated. This meta-analysis evaluates the outcomes of robotic and laparoscopic hysterectomy compared to open hysterectomy. Risk groups including the use of uterine manipulators or colpotomy were created.!##!Methods!#!Ovid-Medline and Embase databases were systematically searched in June 2020. No limitation in date of publication or country was made. Subgroup analyses were performed regarding the surgical approach and the endpoints OS and DFS.!##!Results!#!30 studies fulfilled the inclusion criteria. Five prospective, randomized-control trials were included. Patients were analyzed concerning the surgical approach [open surgery (AH), laparoscopic surgery (LH), robotic surgery (RH)]. Additionally, three subgroups were created from the LH group: the LH high-risk group (manipulator), intermediate-risk group (no manipulator, intracorporal colpotomy) and LH low-risk group (no manipulator, vaginal colpotomy). Regarding OS, the meta-analysis showed inferiority of LH in total over AH (0.97 [0.96; 0.98]). The OS was significantly higher in LH low risk (0.96 [0.94; 0.98) compared to LH intermediate risk (0.93 [0.91; 0.94]). OS rates were comparable in AH and LH Low-risk group. DFS was higher in the AH group compared to the LH group in general (0.92 [95%-CI 0.88; 0.95] vs. 0.87 [0.82; 0.91]), whereas the application of protective measures (no uterine manipulator in combination with vaginal colpotomy) was associated with increased DFS in laparoscopy (0.91 [0.91; 0.95]).!##!Conclusion!#!DFS and OS in laparoscopy appear to be depending on surgical technique. Protective operating techniques in laparoscopy result in improved minimal invasive survival

Long-memory versus structural breaks: an overview

SIGLEAvailable from TIB Hannover: RR 8460(2001,28) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman