Journal ArticleDOI
A solution to the problem of separation in logistic regression
Georg Heinze,Michael Schemper +1 more
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A procedure by Firth originally developed to reduce the bias of maximum likelihood estimates is shown to provide an ideal solution to separation and produces finite parameter estimates by means of penalized maximum likelihood estimation.Abstract:
The phenomenon of separation or monotone likelihood is observed in the fitting process of a logistic model if the likelihood converges while at least one parameter estimate diverges to +/- infinity. Separation primarily occurs in small samples with several unbalanced and highly predictive risk factors. A procedure by Firth originally developed to reduce the bias of maximum likelihood estimates is shown to provide an ideal solution to separation. It produces finite parameter estimates by means of penalized maximum likelihood estimation. Corresponding Wald tests and confidence intervals are available but it is shown that penalized likelihood ratio tests and profile penalized likelihood confidence intervals are often preferable. The clear advantage of the procedure over previous options of analysis is impressively demonstrated by the statistical analysis of two cancer studies.read more
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Dissertation
Questioned sovereignties: independence referendums and secession in a comparative perspective
Journal ArticleDOI
Excessive supraventricular ectopic activity is indicative of paroxysmal atrial fibrillation in patients with cerebral ischemia.
Mark Weber-Krüger,Klaus Gröschel,Meinhard Mende,Joachim Seegers,Rosine Lahno,Beatrice Haase,Cord-Friedrich Niehaus,Frank T. Edelmann,Gerd Hasenfuß,Rolf Wachter,Raoul Stahrenberg +10 more
TL;DR: ESVEA discriminated PAF from non-PAF beyond clinical factors including LAVI/a’ in patients with cerebral ischemia, and may help selecting patients for extended ECG-monitoring, especially in combination with echocardiographic markerLAVI/ a’.
Journal ArticleDOI
Streptococcus pneumoniae colonization of the nasopharynx is associated with increased severity during respiratory syncytial virus infection in young children
Jaelle C. Brealey,Keith J. Chappell,Sally Galbraith,Emmanuelle Fantino,Jane Gaydon,Sarah Tozer,Paul R. Young,Patrick G. Holt,Patrick G. Holt,Peter D. Sly +9 more
TL;DR: The effect of viral and bacterial co‐detections on disease severity during paediatric ARI is clarified to clarify the clinical significance of interactions between viruses and bacteria.
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Predictors of length of stay in psychiatry: analyses of electronic medical records
TL;DR: Prospectively defining reimbursement per case might not be feasible in mental health because length of stay cannot be predicted by patient characteristics, so per diem systems should be used.
Journal ArticleDOI
Congenital anomalies, labor/delivery complications, maternal risk factors and their relationship with perfluorooctanoic acid (PFOA)-contaminated public drinking water.
TL;DR: PFOA is not associated with increased risk of congenital anomalies, most labor and delivery complications and maternal risk factors and additional research is required to assess the observed associations between PFOA, anemia and dysfunctional labor.
References
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Book
Regression Diagnostics: Identifying Influential Data and Sources of Collinearity
TL;DR: In this article, the authors present a method for detecting and assessing Collinearity of observations and outliers in the context of extensions to the Wikipedia corpus, based on the concept of Influential Observations.
Journal ArticleDOI
Regression Diagnostics: Identifying Influential Data and Sources of Collinearity
TL;DR: This chapter discusses Detecting Influential Observations and Outliers, a method for assessing Collinearity, and its applications in medicine and science.
Journal Article
Statistical methods in cancer research. Volume I - The analysis of case-control studies.
N. E. Breslow,N. E. Day +1 more
Journal ArticleDOI
Bias reduction of maximum likelihood estimates
TL;DR: In this paper, the first-order term is removed from the asymptotic bias of maximum likelihood estimates by a suitable modification of the score function, and the effect is to penalize the likelihood by the Jeffreys invariant prior.
Book
Modelling Survival Data in Medical Research
TL;DR: This paper discusses the design of clinical trials, use of computer software in survival analysis, and some non-parametric procedures for modelling survival data.