2,553 research outputs found
Causality and Association: The Statistical and Legal Approaches
This paper discusses different needs and approaches to establishing
``causation'' that are relevant in legal cases involving statistical input
based on epidemiological (or more generally observational or population-based)
information. We distinguish between three versions of ``cause'': the first
involves negligence in providing or allowing exposure, the second involves
``cause'' as it is shown through a scientifically proved increased risk of an
outcome from the exposure in a population, and the third considers ``cause'' as
it might apply to an individual plaintiff based on the first two. The
population-oriented ``cause'' is that commonly addressed by statisticians, and
we propose a variation on the Bradford Hill approach to testing such causality
in an observational framework, and discuss how such a systematic series of
tests might be considered in a legal context. We review some current legal
approaches to using probabilistic statements, and link these with the
scientific methodology as developed here. In particular, we provide an approach
both to the idea of individual outcomes being caused on a balance of
probabilities, and to the idea of material contribution to such outcomes.
Statistical terminology and legal usage of terms such as ``proof on the balance
of probabilities'' or ``causation'' can easily become confused, largely due to
similar language describing dissimilar concepts; we conclude, however, that a
careful analysis can identify and separate those areas in which a legal
decision alone is required and those areas in which scientific approaches are
useful.Comment: Published in at http://dx.doi.org/10.1214/07-STS234 the Statistical
Science (http://www.imstat.org/sts/) by the Institute of Mathematical
Statistics (http://www.imstat.org
The Influence of Job Satisfaction and Organizational Commitment on Executive Withdrawal and Performance
This research examines the influence of job satisfaction and three dimensions of organizational commitment (i.e., affective, continuance, and normative) on the intention to leave, job search activity, performance, and leadership effectiveness of executives. Job satisfaction and the commitment dimensions were hypothesized to negatively predict the retention-related variables. Results generally supported the hypotheses. Job satisfaction had the strongest relationship, but both affective and continuance commitment showed an incremental effect even in the presence of job satisfaction. We also hypothesized that job satisfaction and affective commitment would positively and continuance commitment would negatively associate with general performance and leadership. As predicted, job satisfaction associated positively with performance, though not with leadership. Continuance commitment negatively associated with both performance and leadership
Topological derivation of shape exponents for stretched exponential relaxation
In homogeneous glasses, values of the important dimensionless
stretched-exponential shape parameter beta are shown to be determined by magic
(not adjusted) simple fractions derived from fractal configuration spaces of
effective dimension d* by applying different topological axioms (rules) in the
presence (absence) of a forcing electric field. The rules are based on a new
central principle for defining glassy states: equal a priori distributions of
fractal residual configurational entropy. Our approach and its beta estimates
are fully supported by the results of relaxation measurements involving many
different glassy materials and probe methods. The present unique topological
predictions for beta typically agree with observed values to ~ 1% and indicate
that for field-forced conditions beta should be constant for appreciable ranges
of such exogenous variables as temperature and ionic concentration, as indeed
observed using appropriate data analysis. The present approach can also be
inverted and used to test sample homogeneity and quality.Comment: Original 13 pages lengthened to 21 pages (longer introduction, added
references and discussion of new experimental data published since original
submission
The Nature of the New Employment Relationship(s): A Content Analysis of the Practitioner and Academic Literatures
This article seeks to provide HRM professionals information and guidance that will assist them in understanding, evaluating, and applying current thinking regarding the new employment relationship. The focus of the article is a study that investigates the extent to which there is a consensus in the literature regarding the nature of the new employment relationship by systematically analyzing the content of relevant articles. The discussion incorporates empirical findings from other studies, notes differences between the articles found in scholarly publications versus those found in trade magazines, provides recommendations for HRM professionals, and suggests areas of future research
Determination of solid mass fraction in partially frozen hydrocarbon fuels
Filtration procedures alone are insufficient to determine the amounts of crystalline solid in a partially frozen hydrocarbon distillate fraction. This is due to the nature of the solidification process by which a large amount of liquid becomes entrapped within an interconnected crystalline structure. A technique has been developed to supplement filtration methods with an independent determination of the amount of liquid in the precipitate thereby revealing the actual value of mass percent crystalline solid, %S. A non-crystallizing dye is injected into the fuel and used as a tracer during the filtration. The relative concentrations of the dye in the filtrate and precipitate fractions is subsequently detected by a spectrophotometric comparison. The filtration apparatus was assembled so that the temperature of the sample is recorded immediately above the filter. Also, a second method of calculation has been established which allows significant reduction in test time while retaining acceptable accuracy of results. Data have been obtained for eight different kerosene range hydrocarbon fuels
Can the Relationship between Doctors and Drug Companies Ever Be a Healthy One?
Emma D'Arcy and Ray Moynihan debate whether doctors and drug companies can form healthy alliances or whether these will always be prone to the corrupting influence of drug company money
Performance characterization tests of three 0.44-N (0.1 lbf) hydrazine catalytic thrusters
The 0.44-N (0.1-lbf) class of hydrazine catalytic thruster has been evaluated to assess its capability for spacecraft limit-cycle attitude control with thruster pulse durations on the order of 10 milliseconds. Dynamic-environment and limit-cycle simulation tests were performed on three commercially available thruster/valve assemblies, purchased from three different manufacturers. The results indicate that this class of thruster can sustain a launch environment and, when properly temperature-conditioned, can perform limit-cycle operations over the anticipated life span of a multi-year mission. The minimum operating temperature for very short pulse durations was determined for each thruster. Pulsing life tests were then conducted on each thruster under a thermally controlled condition which maintained the catalyst bed at both a nominal 93 C (200 F) and 205 C (400 F). These were the temperatures believed to be slightly below and very near the minimum recommended operating temperature, respectively. The ensuing life tests ranged from 100,000 to 250,000 pulses at these temperatures, as would be required for spacecraft limit-cycle attitude control applications
The Glass Transition Temperature of Water: A Simulation Study
We report a computer simulation study of the glass transition for water. To
mimic the difference between standard and hyperquenched glass, we generate
glassy configurations with different cooling rates and calculate the
dependence of the specific heat on heating. The absence of crystallization
phenomena allows us, for properly annealed samples, to detect in the specific
heat the simultaneous presence of a weak pre-peak (``shadow transition''), and
an intense glass transition peak at higher temperature.
We discuss the implications for the currently debated value of the glass
transition temperature of water. We also compare our simulation results with
the Tool-Narayanaswamy-Moynihan phenomenological model.Comment: submitted to Phys. Re
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