BACKGROUND We have observed that the area under the receiver operating characteristic curve (AUC) is increasingly being used to evaluate whether a novel predictor should be incorporated in a multivariable model to predict risk of disease. Frequently, investigators will approach the issue in two distinct stages: first, by testing whether the new predictor variable is significant in a multivariab...

We study the consequences of using an error-laden proxy W for instruments Z on the interpretation of Wald, local instrumental variables (LIV), and instrumental variables (IV) estimands in ordered discrete choice structural systems with heterogeneity. A proxy W need only satisfy an exclusion restriction and that the treatment and outcome are mean independent from W given Z. Unlike Z, W need not ...

This paper considers inference on functionals of semi/nonparametric conditional moment restrictions with possibly nonsmooth generalized residuals, which include all of the (nonlinear) nonparametric instrumental variables (IV) as special cases. For these models it is often difficult to verify whether a functional is regular (i.e., root-n estimable) or irregular (i.e., slower than root-n estimabl...

BACKGROUND The onset of schizophrenia is associated with genetic, symptomatic, social and environmental risk factors. The aim of the present study was to determine which environmental factors may contribute to a prediction of a first psychotic episode in subjects at Ultra High Risk (UHR) for developing psychosis. METHOD We included 72 UHR subjects and followed them over a period of 36 months,...

Some recent research has confirmed that the standard Wald (normal) confidence interval approximation for the binomial proportion is inadequate in key respects, especially for extreme values of p . Even for moderately large values of n the coverage probabilities can prove to be erratic for various specific values of p . This fact makes general rules for the use of the Wald method problematic. Al...