Selection bias and misclassification in case–control studies conducted using the National Violent Death Reporting System

Conducting case–control studies using the National Violent Death Reporting System (NVDRS) has the potential to introduce selection bias and misclassification through control selection. Some studies that use NVDRS compare groups of individuals who died by one mechanism, intent or circumstance, to individuals who died by another mechanism, intent or circumstance. For aetiological studies within NVDRS, the use of controls who had a different type of violent death has the potential to introduce selection bias, while relying on narrative summaries for exposure measurement may result in misclassification. We discuss these two methodological issues, and identify an unusual circumstance in which selection of live controls within NVDRS can be employed.

A commentary on ‘A systematic review examining the association between body image and infant feeding methods (breastfeeding vs. bottle-feeding)’

A systematic review is a valuable and influential research method that aims to identify and synthesize all literature relevant to the research question at hand. A well-conducted systematic review benefits the scientific community by providing a summary of all the existing evidence as well as generating new hypotheses and highlighting gaps in the literature. However, when a systematic review does not adhere to the recommended guidelines, it may introduce selection bias and generate false conclusions. Here, we present a commentary on a systematic review by the scholars Morley-Hewitt and Owen titled ‘ A systematic review examining the association between female body image and the intention, initiation, and duration of postpartum infant feeding methods (breastfeeding vs. bottle-feeding)’ that included nine peer-reviewed articles but missed at least eight other peer-reviewed articles that aligned with their study aim, and therefore introduced selection bias in the review. To complete the missing piece, we provide a short summary of these additional articles and describe how they align with this systematic review.

Electoral Redistricting and Endogenous Partisan Control

Recent efforts at estimating bias and responsiveness in electoral systems typically proceed by assigning observations to subsamples according to which party controlled the redistricting process. We show this traditional procedure to introduce selection bias into the resulting estimates of bias and responsiveness and present an alternative strategy for estimating these parameters. Using data from the state legislatures, and employing two different measures of partisan control of redistricting, we obtain results that modestly differ from those obtained with the traditional approach. Measures of control of redistricting utilizing information about the partisan intent of redistricting commissions and tribunals are exogenous to the seats-votes relationship.