The assumption of strongly ignorable treatment assignment is required for eliminating selection bias in observational studies. This article investigates how well this assumption is met by various conceptually unique sets of covariates. The methodology we use is a within-study comparison that contrasts results from a randomized experiment and a quasiexperiment that differ only in whether their r...

Random walks have been proposed as a simple method of efficiently searching, or disseminating information throughout, communication and sensor networks. In nature, animals (such as ants) tend to follow correlated random walks, i.e., random walks that are biased towards their current heading. In this paper, we investigate whether or not complementing random walks with directional bias can decrea...

Electron transport properties of pure and Oxygen and/or Methyl substituted pyrene between two semi-infinite Aluminum atomic electrodes have been investigated by means of density functional theory plus the non-equilibrium green’s function method. The electrodes were represented by a slab of Al atoms oriented along the [111] plane. The computations were carried out in the bias voltage range of 0....

It is well known that the symmetry bias much accelerates the vocabulary learning. In particular, the bias helps infants to connect objects with their names easily. However, grammar learning is another important aspect of language acquisition. In this study, we propose that the symmetry bias also would help to acquire grammar rules faster. We employ Iterated Learning Model, and revise it to incl...

The present paper investigates the effectiveness of R&D subsidies given to start-ups. Taking an aggregate view rather than evaluating a single program, we estimate the impact of R&D subsidies on start-ups’ employment growth and their patent output. A unique data set on start-ups in the East German county of Thuringia allows us to focus on those start-ups that conduct R&D within the first three ...

health consequences of industrialization and urbanization. This interpretation, however, relies on sources subject to selection bias. Our meta-analysis shows that the declining height during industrialization emerges primarily in selected samples. We also develop a parsimonious diagnostic test that reveals, but does not correct for, selection bias in height samples. When applied to four represe...

This study investigated attentional biases in children with asthma. The study aimed at testing whether children with asthma are vigilant to asthma and/or anxiety cues. Thirty-six children (18 with asthma and 18 healthy controls) aged 9-12 completed a computerised dot probe task designed to measure attentional bias to three different categories of words: asthma, anxiety symptom and general negat...

Data from Twitter have been employed in prior research to study the impact of events. Historically, researchers have relied on keyword-based samples of tweets to create a panel of Twitter users that mention event-related keywords during and/or after an event. There are limitations to the keywordbased panel approach. First, the technique suffers from selection bias since users who discuss an eve...

Recent empirical literature documents value-destroying \crosssubsidization" among the divisions of diversi ̄ed ̄rms. However, this literature relies upon two maintained hypotheses: that divisions of diversi ̄ed ̄rms are randomly allocated to their corporate parents and that the investment opportunities facing conglomerate divisions are identical to those of stand-alone ̄rms in their industries. T...

When searching for populations of rare and/or weak signals in noisy data, it is common to use a detection threshold to remove marginal events which are unlikely to be the signals of interest; or a detector might have limited sensitivity, causing it to not detect some of the population. In both cases a selection of data has occurred, which can potentially bias any inferences drawn from the remai...