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Biasing Effect (biasing + effect)

Distribution by Scientific Domains

Psychology	50%

Selected Abstracts

Taxon combinations, parsimony analysis (PAUP*), and the taxonomy of the yellow-tailed woolly monkey, Lagothrix flavicauda

AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 3 2008
Luke J. Matthews
Abstract The classifications of primates, in general, and platyrrhine primates, in particular, have been greatly revised subsequent to the rationale for taxonomic decisions shifting from one rooted in the biological species concept to one rooted solely in phylogenetic affiliations. Given the phylogenetic justification provided for revised taxonomies, the scientific validity of taxonomic distinctions can be rightly judged by the robusticity of the phylogenetic results supporting them. In this study, we empirically investigated taxonomic-sampling effects on a cladogram previously inferred from craniodental data for the woolly monkeys (Lagothrix). We conducted the study primarily through much greater sampling of species-level taxa (OTUs) after improving some character codings and under a variety of outgroup choices. The results indicate that alternative selections of species subsets from within genera produce various tree topologies. These results stand even after adjusting the character set and considering the potential role of interobserver disagreement. We conclude that specific taxon combinations, in this case, generic or species pairings, of the primary study group has a biasing effect in parsimony analysis, and that the cladistic rationale for resurrecting the Oreonax generic distinction for the yellow-tailed woolly monkey (Lagothrix flavicauda) is based on an artifact of idiosyncratic sampling within the study group below the genus level. Some recommendations to minimize the problem, which is prevalent in all cladistic analyses, are proposed. Am J Phys Anthropol, 2008. © 2008 Wiley-Liss, Inc. [source]

Accountability and the Camera Perspective Bias in Videotaped Confessions

ANALYSES OF SOCIAL ISSUES & PUBLIC POLICY, Issue 1 2001
G. Daniel Lassiter
Prior research indicates that altering the perspective from which a videotaped confession is recorded influences assessments of the confession's voluntariness. The present study examined whether increasing decision makers' sense of accountability attenuates this biasing effect of camera perspective. Participants in a high-accountability (but not a low-accountability) condition were told that they would have to justify their judgments concerning the voluntary status of a video-taped confession to a trial judge. Although supplementary measures indicated that high-accountability participants processed information contained in the video-taped confession more carefully and thoroughly, the camera perspective bias persisted. This result adds to a growing body of work indicating that the criminal justice system needs to be seriously concerned with how it acquires and utilizes videotaped confession evidence. [source]

Ratio Estimation with Measurement Error in the Auxiliary Variate

BIOMETRICS, Issue 2 2009
Timothy G. Gregoire
Summary With auxiliary information that is well correlated with the primary variable of interest, ratio estimation of the finite population total may be much more efficient than alternative estimators that do not make use of the auxiliary variate. The well-known properties of ratio estimators are perturbed when the auxiliary variate is measured with error. In this contribution we examine the effect of measurement error in the auxiliary variate on the design-based statistical properties of three common ratio estimators. We examine the case of systematic measurement error as well as measurement error that varies according to a fixed distribution. Aside from presenting expressions for the bias and variance of these estimators when they are contaminated with measurement error we provide numerical results based on a specific population. Under systematic measurement error, the biasing effect is asymmetric around zero, and precision may be improved or degraded depending on the magnitude of the error. Under variable measurement error, bias of the conventional ratio-of-means estimator increased slightly with increasing error dispersion, but far less than the increased bias of the conventional mean-of-ratios estimator. In similar fashion, the variance of the mean-of-ratios estimator incurs a greater loss of precision with increasing error dispersion compared with the other estimators we examine. Overall, the ratio-of-means estimator appears to be remarkably resistant to the effects of measurement error in the auxiliary variate. [source]

Longitudinal analysis when the experimenter does not determine when treatment ends: what is dose,response?

CLINICAL PSYCHOLOGY AND PSYCHOTHERAPY (AN INTERNATIONAL JOURNAL OF THEORY & PRACTICE), Issue 6 2003
Daniel J. Feaster
The most appropriate amount of psychotherapy to address a particular problem is of interest to clinicians, consumers and those responsible for funding of care. The dose,response relationship has been examined within the context of randomized clinical trials, meta-analysis as well as naturalistic studies; however, each of these approaches has limits. Many of these approaches have conceptually blurred two distinct concepts: do participants with different characteristics need different amounts of therapy and do otherwise equal participants show different outcomes when given different levels of (a particular type of) therapy? For any study design, if the experimenter does not determine the duration of therapy, then the length of therapy is said to be endogenous. This endogeneity can bias any attempt to untangle the answer to these two questions. An extension of the biasing effect of this endogeneity involves the choice of times to assess outcome; if outcome assessment depends on when therapy is terminated (rather than exogenously chosen) then estimates of the trajectory of outcome may be biased. Design considerations to minimize this effect are discussed.,Copyright © 2003 John Wiley & Sons, Ltd. [source]