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Results for “model credibility”

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At least 73 records · Page 4Linked to original sources

PubMed1989

Prevention of alcohol use and abuse in adolescence: teacher- vs peer-led intervention.

The use of peer leaders as facilitators for smoking and alcohol abuse prevention with adolescents is one component of recently successful programs. Peer leaders are unique in their abilities to influence peer group behavior because they are members of the peer group, are credible role models and disseminators of social information, and utilize the same language as their peers. Peer leaders can be trained to modify environmental, personality, and behavioral factors that are predictive of alcohol use among adolescents, and become a viable alternative to teachers and adult leaders. The WHO Collaborative Study on Alcohol Education and Young People compared a peer-led alcohol educational program to a teacher-led program to no program in 25 schools in Australia, Chile, Norway, and Swaziland. The educational program emphasized refusal skills for alcohol use among 8th and 9th graders in the four countries. The peer-led educational program appears to be efficacious in reducing adolescent involvement with alcohol across a variety of settings, economies, and cultures. Peer leadership may be a particularly promising approach to prevention, theoretically and empirically.

Adolescent↗

PubMed1997

Electric-field ion cyclotron resonance.

We consider the possibility that DC magnetic fields can interact in a resonant manner with endogenous AC electric fields in biological systems. Intrinsic electric-field ion cyclotron resonance (ICR) interactions would be more physically credible than models based on external AC magnetic fields and might be expected as an evolutionary response to the long-term constancy of the geomagnetic field.

Animals↗

PubMed1990

Fish consumption advisories: toward a unified, scientifically credible approach.

A model is proposed for fish consumption advisories based on consensus-derived risk assessment values for common contaminants in fish and the latest risk assessment methods. The model accounts in part for the expected toxicity to mixtures of chemicals, the underlying uncertainties in the health and exposure data, and the amount of contaminated fish consumed. Application of the model to a larger number of chemicals is possible. Noncancer toxicity is used as an example, but this model is applicable for risks from cancer as well. A second related model is proposed that is useful for comparing potential risks among sites (e.g., rivers and lakes).

Animals↗

PubMed1995

A diagnostic and prognostic tool for epidemiologic and economic analyses of dairy herd health management.

A computer program framework was established to enable a dairy herd production consultant to perform whole-herd analysis. The diagnostic process was an extensive data analysis 1) to derive key parameters related to production, reproduction, and health and 2) to produce input to a prognostic process. The prognostic process synthesized the obtained information into short- or long-term prognoses for the herd through a complex herd simulation model. Site specificity of parameter estimation and forecasting and explorability of assumptions and results were major characteristics of the approach. A user acceptance problem related to the simulation was addressed through a simultaneous process of development and validation during the introduction of the program framework into veterinary practices. The generally slow adoption of herd simulation models in extension work could be due to lack of credibility of the models. A major barrier to adoption of the current whole-herd approach may be the considerable time required to understand and use the tools properly. An example of a simulation experiment based on data from a New York dairy farm was provided, and the interpretation and practical applications of such simulations were discussed.

Animals↗

PubMedDate not supplied

Potentiation of inhaled staphylococcal enterotoxin B-induced toxicity by lipopolysaccharide in mice.

Nonhuman primates are the established model for evaluating toxic responses to staphylococcal enterotoxins (SEs), as they react similarly to humans. Rodents are generally considered unresponsive to SEs. Binding affinities and T-cell reactivity suggest that SE binds more efficiently to primate major histocompatability complex class II receptors than to mouse receptors. We investigated the potentiation of staphylococcal enterotoxin B (SEB) inhalation toxicity by lipopolysaccharide (LPS) in BALB/c mice. Lethality occurred only when SEB was potentiated by LPS. Neither SEB nor LPS produced lethal effects alone. Temporal responses of interleukin 1 alpha, tumor necrosis factor alpha, interleukin 2, and interferon-gamma evoked by inhaled SEB were enhanced by LPS. By 24 hr after intoxication, serum cytokines decreased to baseline levels, and consistent pulmonary perivascular leukocytic infiltrates were evident histologically. Histologic lesions induced by inhalation exposure to SEB by mice, with or without potentiation by LPS, were similar to those in the rhesus monkey. Predominant pulmonary lesions included severe, diffuse interstitial and alveolar pulmonary edema, leukocytic infiltrates, mild perivascular edema, and alveolar fibrin deposition. Although the mechanism of aerosolized SEB-induced toxicity has not been completely resolved, similarities in histologic lesions, cytokine responses, and acute dose-response suggest the LPS-potentiated mouse model may be a credible alternative to the nonhuman primate model.

Animals↗

PubMedDate not supplied

Effect of differentiation of self on adolescent risk behavior: test of the theoretical model.

BACKGROUND: Innovative theoretical models are needed to explain the occurrence of high-risk sexual behaviors, alcohol and other-drug (AOD) use, and academic engagement among ethnically diverse, inner-city adolescents. OBJECTIVE: The aim of this study was to test the credibility of a theoretical model based on the Bowen family systems theory to explain adolescent risk behavior. Specifically tested was the relationship between the predictor variables of differentiation of self, chronic anxiety, and social problem solving and the dependent variables of high-risk sexual behaviors, AOD use, and academic engagement. METHODS: An ex post facto cross-sectional design was used to test the usefulness of the theoretical model. Data were collected from 161 racially/ethnically diverse, inner-city high school students, 14 to 19 years of age. Participants completed self-report written questionnaires, including the Differentiation of Self Inventory, State-Trait Anxiety Inventory, Social Problem Solving for Adolescents, Drug Involvement Scale for Adolescents, and the Sexual Behavior Questionnaire. RESULTS: Consistent with the model, higher levels of differentiation of self related to lower levels of chronic anxiety (p < .001) and higher levels of social problem solving (p < .01). Higher chronic anxiety was related to lower social problem solving (p < .001). A test of mediation showed that chronic anxiety mediates the relationship between differentiation of self and social problem solving (p < .001), indicating that differentiation influences social problem solving through chronic anxiety. Higher levels of social problem solving were related to less drug use (p < .05), less high-risk sexual behaviors (p < .01), and an increase in academic engagement (p < .01). CONCLUSIONS: Findings support the theoretical model's credibility and provide evidence that differentiation of self is an important cognitive factor that enables adolescents to manage chronic anxiety and motivates them to use effective problem solving, resulting in less involvement in health-comprising behaviors and increased academic engagement.

Adolescent↗

PubMed1998

Diffusion-limited, but not perfusion-limited, compartmental models describe cerebral nitrous oxide kinetics at high and low cerebral blood flows.

This study aimed to evaluate the relative importance of diffusion-limited vs. perfusion-limited mechanisms in compartmental models of blood-tissue inert gas exchange in the brain. Nitrous oxide concentrations in arterial and brain efferent blood were determined using gas chromatographic analysis during and after 15 min of nitrous oxide inhalation, at separate low and high steady states of cerebral blood flow (CBF) in five sheep under halothane anesthesia. Parameters and model selection criteria of various perfusion- or diffusion-limited structural models of the brain were estimated by simultaneous fitting of the models to the mean observed brain effluent nitrous oxide concentration for both blood flow states. Perfusion-limited models returned precise, credible estimates of apparent brain volume but fit the low CBF data poorly. Diffusion-limited models provided better overall fit of the data, which was best described by exchange of nitrous oxide between a perfusion-limited brain compartment and an unperfused compartment. In individual animals, during the low CBF state, nitrous oxide kinetics displayed either fast, perfusion-limited behavior or slow, diffusion-limited behavior. This variability was exemplified in the different parameter estimates of the diffusion limited models fitted to the individual animal data sets. Results suggest that a diffusion limitation contributes to cerebral nitrous oxide kinetics.

Anesthetics, Inhalation↗

PubMedDate not supplied

Improving the quality of data used in environmental economics research.

Valuing environmental goods through contingent valuation and through other survey techniques is difficult because of the lack of traditional markets for those goods. EPA provides leadership in overcoming these challenges, using focus groups, workshops, handbooks, and teams of distinguished economists to obtain more reliable economic data from the surveys. Agency economists have provided leadership in employing production economics tools to identify win-win approaches to solve pervasive and neglected environmental problems. In addition, we exploit the speed of sophisticated computers, building field runoff models into economic models and aggregating results from tens of thousands of field sites. These very flexible models provide much more credible, site-specific analyses than previous models, and they offer flexible and efficient remedies to support Total Maximum Daily Loads and other new programs.

Agriculture↗

PubMed2007

Person-centered nursing practice with older people in Ireland.

This column presents an analysis of McCormack's conceptual framework for person-centered practice with older people as a theoretical basis for the delivery of care of older adults in an Irish context. The evaluative process is guided by the framework proposed by Fawcett (2000) for the analysis and evaluation of conceptual models of nursing. The historical evolution, philosophical claims, and an overview of the content of the model are addressed. The following criteria are then applied: logical congruence, the generation of the theory, the credibility of the model, and the contribution of the model to the discipline of nursing.

Aged↗

PubMed2005

Partitioned Bayesian analyses, partition choice, and the phylogenetic relationships of scincid lizards.

Partitioned Bayesian analyses of approximately 2.2 kb of nucleotide sequence data (mtDNA) were used to elucidate phylogenetic relationships among 30 scincid lizard genera. Few partitioned Bayesian analyses exist in the literature, resulting in a lack of methods to determine the appropriate number of and identity of partitions. Thus, a criterion, based on the Bayes factor, for selecting among competing partitioning strategies is proposed and tested. Improvements in both mean -lnL and estimated posterior probabilities were observed when specific models and parameter estimates were assumed for partitions of the total data set. This result is expected given that the 95% credible intervals of model parameter estimates for numerous partitions do not overlap and it reveals that different data partitions may evolve quite differently. We further demonstrate that how one partitions the data (by gene, codon position, etc.) is shown to be a greater concern than simply the overall number of partitions. Using the criterion of the 2 ln Bayes factor > 10, the phylogenetic analysis employing the largest number of partitions was decisively better than all other strategies. Strategies that partitioned the ND1 gene by codon position performed better than other partition strategies, regardless of the overall number of partitions. Scincidae, Acontinae, Lygosominae, east Asian and North American "Eumeces" + Neoseps; North African Eumeces, Scincus, and Scincopus, and a large group primarily from sub-Saharan Africa, Madagascar, and neighboring islands are monophyletic. Feylinia, a limbless group of previously uncertain relationships, is nested within a "scincine" clade from sub-Saharan Africa. We reject the hypothesis that the nearly limbless dibamids are derived from within the Scincidae, but cannot reject the hypothesis that they represent the sister taxon to skinks. Amphiglossus, Chalcides, the acontines Acontias and Typhlosaurus, and Scincinae are paraphyletic. The globally widespread "Eumeces" is polyphyletic and we make necessary taxonomic changes.

Animals↗

PubMed1999

Parsimonious modelling of water and suspended sediment flux from nested catchments affected by selective tropical forestry.

The ability to model the suspended sediment flux (SSflux) and associated water flow from terrain affected by selective logging is important to the establishment of credible measures to improve the ecological sustainability of forestry practices. Recent appreciation of the impact of parameter uncertainty on the statistical credibility of complex models with little internal state validation supports the use of more parsimonious approaches such as data-based mechanistic (DBM) modelling. The DBM approach combines physically based understanding with model structure identification based on transfer functions and objective statistical inference. Within this study, these approaches have been newly applied to rainfall-SSflux response. The dynamics of the sediment system, together with the rainfall-river flow system, were monitored at five nested contributory areas within a 44 ha headwater region in Malaysian Borneo. The data series analysed covered a whole year at a 5 min resolution, and were collected during a period some five to six years after selective timber harvesting had ceased. Physically based and statistical interpretation of these data was possible given the wealth of contemporary and past hydrogeomorphic data collected within the same region. The results indicated that parsimonious, three-parameter models of rainfall-river flow and rainfall-SSflux for the whole catchment describe 80 and 90% of the variance, respectively, and that parameter changes between scales could be explained in physically meaningful terms. Indeed, the modelling indicated some new conceptual descriptions of the river flow and sediment-generation systems. An extreme rainstorm having a 10-20 year return period was present within the data series and was shown to generate new mass movements along the forestry roads that had a differential impact on the monitored contributory areas. Critically, this spatially discrete behaviour was captured by the modelling and may indicate the potential use of DBM approaches for (i) predicting the differential effect of alternative forestry practices, (ii) estimating uncertainty in the behaviour of ungauged areas and (iii) forecasting river flow and SSflux in terrain with temporal changes in rainfall regime and forestry impacts.

Ecosystem↗

PubMed2003

The Neuman Systems Model Institute: testing middle-range theories.

The credibility of the Neuman systems model can only be established through the generation and testing of Neuman systems model-derived middle-range theories. However, due to the number and complexity of Neuman systems model concepts/concept interrelations and the diversity of middle-range theory concepts linked to these Neuman systems model concepts by researchers, no explicit middle-range theories have yet been derived from the Neuman systems model. This article describes the development of an organized program for the systematic study of the Neuman systems model. Preliminary work, already accomplished, is detailed, and a tentative plan for the completion of further preliminary work as well as beginning the actual research conduction phase is proposed.

Academies and Institutes↗

PubMed2001

Deriving a risk-adjustment model for pressure ulcer development using the Minimum Data Set.

OBJECTIVE: To use the Minimum Data Set (MDS) to derive a risk-adjustment model for pressure ulcer development that may be used in assessing the quality of nursing home care. DESIGN: Perspective observational study using MDS data from 1997. SETTING: A large, for-profit, nursing home chain. PARTICIPANTS: Our unit of analysis was 39,649 observations made on 14,607 nursing home residents who were without a stage 2 or larger pressure ulcer on an index assessment. MEASUREMENTS: Pressure ulcer status was determined at an outcome assessment approximately 90 days after an index assessment. Potential predictors of pressure ulcer development were examined for bivariate associations, contributing to the development of a multivariate logistic regression model. RESULTS: A stage 2 or larger pressure ulcer developed in 2.3% of the observations. Seventeen resident characteristics were found to be associated with pressure ulcer development. These included dependence in mobility and transferring, diabetes mellitus, peripheral vascular disease, urinary incontinence, lower body mass index, and end-stage disease. A risk-adjustment model based on these characteristics was well calibrated and able to discriminate among residents with different levels of risk for ulcer development (model c-statistic = 0.73). CONCLUSION: A clinically credible risk-adjustment model with good performance properties can be developed using the MDS. This model may be useful in profiling nursing homes on their rate of pressure ulcer development.

Aged↗

PubMed2001

Neuman systems model-based research: an integrative review project.

The project integrated Neuman systems model-based research literature. Two hundred published studies were located. This article is limited to the 59 full journal articles and 3 book chapters identified. A total of 37% focused on prevention interventions; 21% on perception of stressors; and 10% on stressor reactions. Only 50% of the reports explicitly linked the model with the study variables, and 61% did not include conclusions regarding model utility or credibility. No programs of research were identified. Academic courses and continuing education workshops are needed to help researchers design programs of Neuman systems model-based research and better explicate linkages between the model and the research.

Bibliometrics↗

PubMed2004

A Bayesian approach to estimate and validate the false negative fraction in a two-stage multiple screening test.

OBJECTIVES: In estimating sensitivity and specificity of a diagnostic kit it is imperative that all study subjects are verified via a gold standard procedure. However the application of such a procedure to all the study subjects may not be feasible due to associated cost, risk and invasiveness. As a result only a part of the study subjects receive the definitive assessment. The accuracy of a diagnostic kit can also be expressed in terms of its error rates. Our first objective is to estimate the false negative fraction (FNF) under partial verification in a particular case of a two-stage multiple screening test using a beta-binomial model and a Bayesian logistic model. The second objective is to validate the two models in order to determine which fits the data better. METHODS: We estimate the FNF from the above mentioned models using Bayesian approach. The validation of the models is based on their out-of-sample predictive capabilities. RESULTS: For the bowel cancer data that was used in this study we found the median posterior estimate of the FNF, based on the beta-binomial model, to be 26.4% (95% credible interval: 0.123-0.650). The corresponding estimate based on the Bayesian logistic model was 23.3% (95% credible interval: 0.124-0.375). Validation results showed that the betabinomial model gave slightly better predictions compared to the Bayesian logistic model. CONCLUSIONS: Estimation of the FNF can be done by adopting the Bayesian approach. Models fitted can be validated by comparing their performance in terms of their out-of-sample predicitve potential.

Bayes Theorem↗

PubMed2003

The function of credibility in information processing for risk perception.

This study examines how credibility affects the way people process information and how they subsequently perceive risk. Three conceptual areas are brought together in this analysis: the psychometric model of risk perception, Eagly and Chaiken's heuristic-systematic information processing model, and Meyer's credibility index. Data come from a study of risk communication in the circumstance of state health department investigations of suspected cancer clusters (five cases, N = 696). Credibility is assessed for three information sources: state health departments, citizen groups, and industries involved in each case. Higher credibility for industry and the state directly predicts lower risk perception, whereas high credibility for citizen groups predicts greater risk perception. A path model shows that perceiving high credibility for industry and state-and perceiving low credibility for citizen groups-promotes heuristic processing, which in turn is a strong predictor of lower risk perception. Alternately, perceiving industry and the state to have low credibility also promotes greater systematic processing, which consistently leads to perception of greater risk. Between a one-fifth and one-third of the effect of credibility on risk perception is shown to be indirectly transmitted through information processing.

Journal Article↗

PubMed1982

Trajectory formation and handwriting: a computational model.

This paper proposes a computational model for different aspects of trajectory formation, from point-to-point movements to handwriting. The proposed model is based on a mechanism of composition of basic curve elements (strokes) which separates the spatial and the temporal aspects of trajectory formation. At the same time, the model suggests a method for storing and describing arm movements, as a list of stroke descriptors. Experimental trajectories were digitized and analyzed with regard to several types of movements: i) point-to-point trajectories, ii) closed trajectories, iii) trajectories with inflection points, iv) spiral-like trajectories, v) handwritten trajectories. Velocity and curvature profiles were computed for the trajectories and the model was fitted to the data. The implications of the model and its "credibility" in the general context of motor control are discussed.

Arm↗

PubMed2002

Applications of computational toxicology methods at the Agency for Toxic Substances and Disease Registry.

In its efforts to provide consultations to state and local health departments, other federal agencies, health professionals, and the public on the health effects of environmental pollutants, the Agency for Toxic Substances and Disease Registry relies on the latest advances in computational toxicology. The computational toxicology laboratory at the agency is continually engaged in developing and applying models for decision-support tools such as physiologically based pharmacokinetic (PBPK) models, benchmark dose (BMD) models, and quantitative structure-activity relationship (QSAR) models. PBPK models are suitable for connecting exposure scenarios to biological indicators such as tissue dose or end point response. The models are used by the agency to identify the significance of exposure routes in producing tissue levels of possible contaminants for people living near hazardous waste sites. Additionally, PBPK models provide a credible scientific methodology for route-to-route extrapolations of health guidance values, which are usually determined from a very specific set of experiments. Also, scientists at the computational toxicology laboratory are using PBPK models for advancing toxicology research in such areas as joint toxicity assessment and child-based toxicity assessments. With BMD modeling, all the information embedded in an experimentally determined dose-response relationship is used to estimate, with minimum extrapolations, human health guidance values for environmental substances. Scientists in the laboratory also rely on QSAR models in the many cases where consultations from the agency are reported for chemicals that lack adequate experimental documentation.

Benchmarking↗