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Suggested Procedure (suggested + procedure)

Distribution by Scientific Domains

Mathematics and Statistics	50%

Selected Abstracts

A two-stage procedure for comparing hazard rate functions

JOURNAL OF THE ROYAL STATISTICAL SOCIETY: SERIES B (STATISTICAL METHODOLOGY), Issue 1 2008
Peihua Qiu
Summary., Comparison of two hazard rates is important in applications that are related to times to occurrence of a specific event. Conventional comparison procedures, such as the log-rank, Gehan,Wilcoxon and Peto,Peto tests, are powerful only when the two hazard rates do not cross each other. Because crossing hazard rates are common in practice, several procedures have been proposed in the literature for comparing such rates. However, most of these procedures consider only the alternative hypothesis with crossing hazard rates; many other realistic cases, including those when the two hazard rates run parallel to each other, are excluded from consideration. We propose a two-stage procedure that considers all possible alternatives, including ones with crossing or running parallel hazard rates. To define its significance level and p -value properly, a new procedure for handling the crossing hazard rates problem is suggested, which has the property that its test statistic is asymptotically independent of the test statistic of the log-rank test. We show that the two-stage procedure, with the log-rank test and the suggested procedure for handling the crossing hazard rates problem used in its two stages, performs well in applications in comparing two hazard rates. [source]

An introduction to electrocardiogram monitoring

NURSING IN CRITICAL CARE, Issue 1 2010
Phil Jevon
The aim of this paper is to provide an introduction to electrocardiogram (ECG) monitoring. The objectives are to: ,define an ECG; ,describe how the ECG relates to cardiac contraction, with specific reference to the conduction system of the heart; ,recognize sinus rhythm; ,list the indications for ECG monitoring; ,discuss the important features of a modern bedside cardiac monitor; ,describe where to position ECG electrodes; ,outline a suggested procedure for ECG monitoring; ,discuss the infection control issues related to ECG monitoring. [source]

Resolution of two-way data from spectroscopic monitoring of reaction or process systems by parallel vector analysis (PVA) and window factor analysis (WFA): inspection of the effect of mass balance, methods and simulations

JOURNAL OF CHEMOMETRICS, Issue 3 2003
Jian-Hui Jiang
Abstract The effect of mass balance on the analysis of two-way data of reaction or process systems is investigated. It is shown that the rank-deficient species-related bilinear model can be converted to a full-rank reaction-related bilinear model, and in general situations the chemical rank for a system is the number of reactions plus one. Two slightly modified procedures are thus suggested to extract the spectral subspaces essential for resolution and to ascertain the number of reactions in different time domains. Based on the reaction-related bilinear model, a procedure of window factor analysis (WFA) is implemented for resolving the extent curves of reactions. A new two-way resolution approach, parallel vector analysis (PVA), is also developed. The idea of PVA is to construct a set of subspaces comprising only one common (spectral) component and then find a vector that is in parallel with a series of vectors coming from different subspaces. With suitably constructed subspaces the PVA procedure offers a versatile avenue to approach the unique resolution of spectral profiles. A four-component system which comprises four different processes or reactions is simulated. Results obtained reveal that favorable resolution is achieved for the spectral and concentration profiles by the suggested procedures of WFA and PVA. Copyright © 2003 John Wiley & Sons, Ltd. [source]

A Solution to the Problem of Monotone Likelihood in Cox Regression

BIOMETRICS, Issue 1 2001
Georg Heinze
Summary. The phenomenon of monotone likelihood is observed in the fitting process of a Cox model if the likelihood converges to a finite value while at least one parameter estimate diverges to ±,. Monotone likelihood primarily occurs in small samples with substantial censoring of survival times and several highly predictive covariates. Previous options to deal with monotone likelihood have been unsatisfactory. The solution we suggest is an adaptation of a procedure by Firth (1993, Biometrika80, 27,38) originally developed to reduce the bias of maximum likelihood estimates. This procedure produces finite parameter estimates by means of penalized maximum likelihood estimation. Corresponding Wald-type tests and confidence intervals are available, but it is shown that penalized likelihood ratio tests and profile penalized likelihood confidence intervals are often preferable. An empirical study of the suggested procedures confirms satisfactory performance of both estimation and inference. The advantage of the procedure over previous options of analysis is finally exemplified in the analysis of a breast cancer study. [source]