10,284 research outputs found
MANOVA modelling of a chiropractic longitudinal study using multiple imputation
No full textThe purpose of this report is to present the detailed statistical analysis of a randomised, placebo-controlled trial comparing two different treatment modalities to an intervention of no known benefit for people with acute or subacute thoracic spine pain.
The therapy arms consist of Spinal Manipulative Therapy (SMT) and Graston Technique (GT) and the placebo is a non-functional ultrasound. A placebo group was utilised because at present there are no proven treatments for non-specific thoracic pain. This trial is registered with the Australia and New Zealand Clinical Trials Registry. Ethics approval has been granted by Murdoch University Human Research and Ethics Committee, number 2007/274.
The aim of this three arm trial was to test the efficacy of SMT and GT as independent modalities compared to detuned ultrasound for the outcomes of pain and disability. The latter were measured using the Visual Analogue Scale (VAS) and a modified Oswestry Back Pain Disability Index. The study was conducted at the Murdoch University Chiropractic student clinic in Perth, Australia, and the protocol published in Crothers et al (2008).
In this report, Section 2 provides an initial exploratory analysis of the data, Section 3 outlines the statistical models used in the final analysis, Section 4 defines these models in mathematical terms, Section 5 discusses the management of missing values via multiple imputation and Section 6 presents the results of the statistical modelling and hypothesis tests. The clinical study will be published in full elsewhere
The missing field
No full textPublished work by a Douglas College Student Alumni. Jennifer Zilm's poetry collection, "The Missing Field", concerns themes of translation, preservation and the engagement with the transitory documents of everyday life, whether a snapshot of a Vancouver bus, postcards from the Middle East, lecture notes on Euripides, a van Gogh museum catalogue or marginalia in water damaged collection of Rilke poems. Part of the "Essential poets (255)" series. --Provided by publisher.Poems© Author
State Estimation of Linear Systems With Sparse Inputs and Markov-Modulated Missing Outputs
No full textIn this paper, we consider the problem of estimating the states of a linear dynamical system whose inputs are jointly sparse and outputs at a few unknown time instants are missing. We model the missing data mechanism using a Markov chain with two states representing the missing and non-missing data. This mechanism with memory governed by the Markov chain models intermittent outages due to communication channels and occlusions corresponding to moving objects. We rely on the sparse Bayesian learning framework to derive an estimation algorithm that uses Kalman smoothing to handle temporal correlation and the Viterbi algorithm to handle missing data. Further, we demonstrate the utility of our algorithm by applying it to the frequency division duplexed multiple input multiple output downlink channel estimation problem.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Signal Processing System
How do new product development startups handle missing expertise?
No full textThis paper presents a framework for how new product development focused startup firms (NPDSF) handle missing expertise. The dimensions of the framework are: strategies for handling missing expertise, channels used to acquire missing expertise, and a priori awareness, timing and nature of missing expertise. Each dimension was analyzed in the context of data collected through interviews with entrepreneurs at NPDSFs. Obtaining free advice from experts and attempting to develop the missing expertise internally were the most frequently used strategies. Product development team’s own social and professional network was the most frequently used channel. Moreover, the results suggest that if an NPDSF does not anticipate the missing expertise, it will most likely run into it unprepared during the development phase of the new product development process. On the other hand, if it anticipates the missing expertise, it will most likely handle it during the planning phase by making structural changes to its product vision and operations. Therefore, being able to anticipate missing expertise might increase NPDSF success. The framework that was developed in the study can be leveraged in guiding future research.Product Innovatie ManagementIndustrial Design Engineerin
Making noisy data sing : a micro approach to measuring industrial efficiency
No full textTechnical, scale and allocative inefficiency are widely believed to plague the industrial sectors of developing countries. This paper presents a way to measure this inefficiency with imperfect data. There is great interest in documenting the patterns and magnitudes of inefficiency, so that appropriate corrective policies can be designed. This paper presents a new approach to analyzing plant efficiency that recognizes and deals with such data imperfections as measurement error, missing observations and selectivity bias. The author has developed full-information maximum-likelihood (FIML) estimators of production technologies that deal with missing data and measurement errors, making alternative assumptions about the missing data patterns and the timing of employment and decisions. These estimators yield indices of the returns to scale, means square deviation from the efficient frontier and - when labor is treated as endogenous - mean square deviation from efficient factor mixes. To gauge the performance of the alternative estimators, the author applies them to census data on Chilean industry, and compares the results with naive estimators that do not recognize data imperfections.Economic Theory&Research,Environmental Economics&Policies,Statistical&Mathematical Sciences,Information Technology,Banks&Banking Reform
Systematic reviews with language restrictions and no author contact have lower overall credibility: a methodology study
No full textZhen Wang,1–3 Juan P Brito,4 Apostolos Tsapas,5 Marcio L Griebeler,4 Fares Alahdab,1,3 Mohammad Hassan Murad,1,3,61Robert D and Patricia E Kern Center for the Science of Health Care Delivery, 2Division of Health Care Policy and Research, Department of Health Sciences Research, 3Knowledge and Evaluation Research Unit, 4Division of Endocrinology, Diabetes, Metabolism, and Nutrition, Mayo Clinic, Rochester, MN, USA; 5Aristotle University of Thessaloniki, Thessaloniki, Greece; 6Division of Preventive, Occupational and Aerospace Medicine, Mayo Clinic, Rochester, MN, USABackground: High-quality systematic reviews (SRs) require rigorous approaches to identify, appraise, select, and synthesize research evidence relevant to a specific question. In this study, we evaluated the association between two steps in the conduct of an SR – restricting the search to English, and author contact for missing data – and the overall credibility of a SR.Methods: All SRs cited by the Endocrine Society's Clinical Practice Guidelines published from October 2006 through January 2012 were included. The main outcome was the overall A Measurement Tool to Assess Systematic Reviews (AMSTAR) score, as a surrogate of SR credibility. Nonparametric Kruskal–Wallis tests and multivariable linear regression models were used to investigate the association between language restriction, author contact for missing data, and the overall AMSTAR score.Results: In all, 69 SRs were included in the analysis. Only 31 SRs (45%) reported searching non-English literature, with an average AMSTAR score of 7.90 (standard deviation [SD] =1.64). SRs that reported language restriction received significantly lower AMSTAR scores (mean =5.25, SD =2.32) (P<0.001). Only 30 SRs (43%) reported contacting authors for missing data, and these received, on average, 2.59 more AMSTAR points (SD =1.95) than those who did not (P<0.001). In multivariable analyses, AMSTAR score was significantly correlated with language restriction (beta =-1.31, 95% confidence interval [CI]: -2.62, -0.01, P=0.05) and author contact for missing data (beta =2.16, 95% CI: 0.91, 3.41, P=0.001). However, after adjusting for compliance with reporting guidelines, language restriction was no longer significantly associated with the AMSTAR score.Conclusion: Fewer than half of the SRs conducted to support the clinical practice guidelines we examined reported contacting study authors or searched non–English literature. SRs that did not conduct these two steps had lower quality scores, suggesting the importance of these two steps for overall SR credibility.Keywords: evidence-based medicine, research design, validity, quality of evidenc
Assessing Methods for Handling Missing Data Using an LSTM Deep Learning Model in Traffic Forecasting
No full textDue to the increasing popularity of various types of sensors in traffic management, it has become significantly easier to collect data on traffic flow. However, the integrity of these data sets is often compromised due to missing values resulting from sensor failures, communication errors, and other malfunctions. This study investigates the effect of missing data on the performance of Long Short-Term Memory (LSTM) models in traffic flow prediction and assesses strategies to handle these missing values. By actively removing values from a complete data set, three strategies to handle these missing values are evaluated: dropping null values, replacing them with zero, and linear interpolation. We show that LSTM models are surprisingly resilient to missing data, with little impact on prediction accuracy for up to 40% of missing data, irrespective of the strategy used. For higher proportions of missing data, dropping null values leads to significant performance degradation, while zero-filling and interpolation maintain predictive accuracy. This paper provides insights into the choice of missing data handling strategies in time-series prediction tasks, demonstrating the potential of LSTM models for traffic forecasting under less-than-ideal data conditionsCSE3000 Research ProjectComputer Science and Engineerin
Missing issues: a response
No full textjournal articleI am inclined to retitle this article "Missing Issues: One Technique for Doubling Staff, Postage, and Xeroxing Expenses While Needlessly Alienating Vendors." I cannot, of course, be sure it would double expenses as the author does not supply figures, but we utilize the spare moments of one part-time student to fill in a very simple two-part form (without certified mail, return receipts, or Xeroxed copies of previous correspondence) to order our missing issues
Countermeasures of Zero-missing Phenomenon in (E)HV Cable Systems
No full textZero-missing is a phenomenon in shunt compensated cable systems in which the current through the line breaker does not cross the zero point for several cycles. This paper deals with a thorough investigation on countermeasures of the zero-missing phenomenon in transmission systems and determines the requirements, benefits, and risks of applying each method. The effectiveness of countermeasures is studied on a simulated cable project with different cable lengths in an actual grid model of the Dutch 380 kV transmission system. Results are analyzed based on three criteria related to the IEC standards and the Dutch grid code. In addition, the switching sequence of circuit-breakers is specified to maximize the effectiveness of the countermeasures. A statistical switching analysis is performed for the insulation coordination study since the application of some countermeasures increases the probability of high transient switching overvoltages. Moreover, the closing variation threshold of circuit-breakers is calculated as a function of the circuit impedance and the shunt compensation degree.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Intelligent Electrical Power GridsEEMS - Genera
- …
