Zhang Z.,Eunice Kennedy ShriverNational Institute of Child Health and Human Development |
Albert P.S.,Eunice Kennedy ShriverNational Institute of Child Health and Human Development
Biometrics | Year: 2011
It has become increasingly common in epidemiological studies to pool specimens across subjects to achieve accurate quantitation of biomarkers and certain environmental chemicals. In this article, we consider the problem of fitting a binary regression model when an important exposure is subject to pooling. We take a regression calibration approach and derive several methods, including plug-in methods that use a pooled measurement and other covariate information to predict the exposure level of an individual subject, and normality-based methods that make further adjustments by assuming normality of calibration errors. Within each class we propose two ways to perform the calibration (covariate augmentation and imputation). These methods are shown in simulation experiments to effectively reduce the bias associated with the naive method that simply substitutes a pooled measurement for all individual measurements in the pool. In particular, the normality-based imputation method performs reasonably well in a variety of settings, even under skewed distributions of calibration errors. The methods are illustrated using data from the Collaborative Perinatal Project. © 2010, The International Biometric Society No claim to original US government works.
Simpson E.A.,Eunice Kennedy ShriverNational Institute of Child Health and Human Development |
Simpson E.A.,University of Parma |
Paukner A.,Eunice Kennedy ShriverNational Institute of Child Health and Human Development |
Suomi S.J.,Eunice Kennedy ShriverNational Institute of Child Health and Human Development |
And 2 more authors.
Developmental Psychobiology | Year: 2014
Previous studies suggest that about 50% of rhesus macaque infants engage in neonatal imitation of facial gestures. Here we measured whether individual differences in newborn macaques' (n=49) visual attention may explain why some infants imitate lipsmacking (LPS) and tongue protrusion (TP) gestures. LPS imitators, but not TP imitators, looked more to a human experimenter's face and to a control stimulus compared to nonimitators (p=017). LPS imitation was equally accurate when infants were looking at faces and when they were looking away (p=221); TP imitation was more accurate when infants were looking at faces (p=001). Potentially, less attention is necessary for LPS imitation compared to TP imitation, as LPS is part of macaques' natural communicative repertoire. These findings suggest that facial gestures may differentially engage imitators and nonimitators, and infants' visual attention during neonatal assessments may uncover the conditions that support this skill.© 2013 Wiley Periodicals, Inc.