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
Citations
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Re-evaluation of the comparative effectiveness of bootstrap-based optimism correction methods in the development of multivariable clinical prediction models
TL;DR: The effectiveness of the three bootstrap estimators were comparable, but the .632+ estimator performed relatively well under small sample settings, except when the regularized estimation methods are adopted.
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Mixed-Membership of Experts Stochastic Blockmodel
TL;DR: The mixed membership of experts stochastic block model as mentioned in this paper is an extension to the original mixed membership block model, which incorporates covariate actor information into the existing model to allow actors membership to different groups, depending on the interaction in question.
Journal ArticleDOI
Esfenvalerate toxicity to the cladoceran Ceriodaphnia dubia in the presence of green algae, Pseudokirchneriella subcapitata
Susanne M. Brander,Susanne M. Brander,Christopher M. Mosser,Juergen Geist,Michelle L. Hladik,Inge Werner,Inge Werner +6 more
TL;DR: The authors used a modified version of the US EPA WET Ceriodaphnia dubia acute test to investigate the effects of phytoplankton on toxicity of the pyrethroid insecticide, esfenvalerate.
Journal ArticleDOI
Processing plant and machinery sanitation and hygiene practices associate with Listeria monocytogenes occurrence in ready-to-eat fish products
TL;DR: Performing frequent periodic thorough sanitation alongside everyday sanitation practices associated with a decreased risk of product contamination is identified, particularly among the L. monocytogenes positive fish-processing plants.
Journal ArticleDOI
Appropriateness of epinephrine use in ED patients with anaphylaxis
TL;DR: Although more than 60% of anaphylaxis patients did not receive epinephrine in the ED, the allergists-immunologists deemed ED management appropriate in 98% of total cases.
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.