Evaluation of alternative confidence intervals to address non-inferiority through the stratified difference between proportions

The confidence interval (CI) for the difference between two proportions has been an important and active research topic, especially in the context of non-inferiority hypothesis testing. Issues concerning the Type 1 error rate, power, coverage rate and aberrations have been extensively studied for non-stratified cases. However, stratified confidence intervals are frequently used in non-inferiority trials and similar settings. In this paper, several methods for stratified confidence intervals for the difference between two proportions, including existing methods and novel extensions from unstratified CIs, are evaluated across different scenarios. When sparsity across the strata is not a concern, adding imputed observations to the stratification analysis can strengthen Type-1 error control without substantial loss of power. When sparseness of data is a concern, most of the evaluated methods fail to control Type-1 error; the modified stratified t-test CI is an exception. We recommend the modified stratified t-test CI as the most useful and flexible method across the respective scenarios; the modified stratified Wald CI may be useful in settings where sparsity is unlikely. These findings substantially contribute to the application of stratified CIs for non-inferiority testing of differences between two proportions.     

On the estimation of the most probable number in a serial dilution experiment

The purpose of this paper is to present some alternative estimates for the 'most probable number' of bacteria in a serial dilution experiment. These estimates are directed to be less biased than the ordinary maximum likelihood estimate. A numerical example illustrates the extent to which the variance and the mean square error of these estimates are generally less than those corresponding to the maximum likelihood estimate.     

The Dynamic Relationship Between the Dollar and Components of U.S. Trade

The dynamic response of the nominal trade account to changes in the value of the U.S. dollar has been posited to follow a J-curve pattern. Recent experience calls this into question. The aggregate nominal trade balance is decomposed here into four components, both prices and volumes of imports and exports. Time series specification tests and Granger tests of causal priority are employed to identify the existence and nature of the response of each individual component to dollar movements. Surprisingly weak and delayed responses of both import prices and volumes are found, suggesting a new view of trade-balance evolution.     

A note on the analysis of parity progression ratios

Contingency table modeling procedures are proposed to examine the effects of independent variables on parity progression ratios. The methodology is outlined and an incremental-factorial linear model is developed.     

Use of generalized estimating equations in a trial in influenza to explore treatment effects over time

For trials with repeated measurements of outcome, analyses often focus on univariate outcomes, such as analysis of summary measures or of the last on‐treatment observation. Methods which model the whole data set provide a rich source of approaches to analysis. For continuous data, mixed‐effect modelling is increasingly used. For binary and categorical data, models based on use of generalized estimating equations account for intra‐subject correlation and allow exploration of the time course of response, as well as providing a useful way to account for missing data, when such data can be maintained as missing in the analysis. The utility of this approach is illustrated by an example from a trial in influenza. Copyright © 2004 John Wiley & Sons Ltd.     

THE EFFECT OF YOUTH ALCOHOL INITIATION ON HIGH SCHOOL COMPLETION

The social environment inherent in schools impacts both alcohol consumption onset and high school completion. The results reported here, based on data from the 1979–96 NLSY panels, show that the social coincidences between alcohol consumption and education are important determinants of both education completion and alcohol onset. Ignoring the social nature of these simultaneous decisions underestimates the impact of alcohol onset on education. After correcting for the presence of an endogenous positive relationship between schooling and alcohol consumption, we find that alcohol initiation before age 14 significantly reduces the probability of timeously completing high school by between 7% and 22%. (JEL I18 , I21 )     

Eine neuer Weg zur Beschreibung beruflicher Leistung: Eigenverantwortung

Self-responsible behavior is introduced as a new part of work performance. It is defined as an organizational behavior, which should be well adapted to a difficult and extra-ordinary situation lacking a well-defined task. A decreasing frequency of clearly defined tasks and roles is observable because of changes due to general restructuring, cutting off hierarchy levels and out-sourcing of major organizational functions. Employees acting in a self-responsible manner face these situations by defining their tasks on their own risk. Other new theories of extra-role behavior (e.g. organizational citizenship behavior, contextual performance or whistle blowing) are classified as either self-responsible or as “carrying out one′s duty” regarding the criteria ‘usefulness for the organization’ and ‘gratuitousness of acts’.