Count Data (count + data)

Distribution by Scientific Domains

Terms modified by Count Data

  • count data models

  • Selected Abstracts


    Real-Time OD Estimation Using Automatic Vehicle Identification and Traffic Count Data

    COMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 1 2002
    Michael P. Dixon
    A key input to many advanced traffic management operations strategies are origin,destination (OD) matricies. In order to examine the possibility of estimating OD matricies in real-time, two constrained OD estimators, based on generalized least squares and Kalman filtering, were developed and tested. A one-at-a-time processing method was introduced to provide an efficient organized framework for incorporating observations from multiple data sources in real-time. The estimators were tested under different conditions based on the type of prior OD information available, the type of assignment available, and the type of link volume model used. The performance of the Kalman filter estimators also was compared to that of the generalized least squares estimator to provide insight regarding their performance characteristics relative to one another for given scenarios. Automatic vehicle identification (AVI) tag counts were used so that observed and estimated OD parameters could be compared. While the approach was motivated using AVI data, the methodology can be generalized to any situation where traffic counts are available and origin volumes can be estimated reliably. The primary means by which AVI data was utilized was through the incorporation of prior observed OD information as measurements, the inclusion of a deterministic link volume component that makes use of OD data extracted from the latest time interval from which all trips have been completed, and through the use of link choice proportions estimated based on link travel time data. It was found that utilizing prior observed OD data along with link counts improves estimator accuracy relative to OD estimation based exclusively on link counts. [source]


    Using Population Count Data to Assess the Effects of Changing River Flow on an Endangered Riparian Plant

    CONSERVATION BIOLOGY, Issue 4 2006
    DIANE M. THOMSON
    análisis de viabilidad poblacional; gestión ribereña; método de difusión; presas; riesgo de extinción Abstract:,Methods for using simple population count data to project extinction risk have been the focus of much recent theoretical work, but few researchers have used these approaches to address management questions. We analyzed 15 years of census data on the federally endangered endemic riparian plant Pityopsis ruthii (Small) with the diffusion approximation (DA). Our goals were to evaluate relative extinction risk among populations in two different watersheds (in Tennessee, U.S.A.) and potential effects of variation in managed river flow on population dynamics. Populations in both watersheds had high projected risks of extinction within 50 years, but the causes of this risk differed. Populations of P. ruthii on the Hiwassee River had higher initial population sizes but significantly lower average growth rates than those on the Ocoee River. The only populations with low predicted short-term extinction risk were on the Ocoee. Growth rates for populations on both rivers were significantly reduced during periods of lower river flow. We found only marginal evidence of a quadratic relationship between population performance and flow. These patterns are consistent with the idea that low flows affect P. ruthii due to growth of competing vegetation, but the degree to which very high flows may reduce population growth is still unclear. Simulations indicated that populations were most sensitive to growth rates in low-flow years, but small changes in the frequency of these periods did not strongly increase risk for most populations. Consistent with results of other studies, DA estimates of extinction risk had wide confidence limits. Still, our results yielded several valuable insights, including the need for greater monitoring of populations on the Hiwassee and the importance of low-flow years to population growth. Our work illustrates the potential value of simple methods for analyzing count data despite the challenges posed by uncertainty in estimates of extinction risk. Resumen:,Los métodos que utilizan datos de conteos simples de la población para proyectar el riesgo de extinción han sido el foco reciente de mucho trabajo teórico, pero pocos investigadores han utilizado estos métodos para responder preguntas de gestión. Analizamos 15 años de datos de censos de la planta ribereña, endémica y federalmente en peligro Pityopsis ruthii (Small) mediante el método de difusión. Nuestras metas fueron evaluar el riesgo de extinción de poblaciones en dos cuencas hidrológicas distintas y con dos efectos potenciales de la variación del flujo de agua sobre la dinámica de la población. Las poblaciones en ambas cuencas tenían alto riesgo de extinción proyectado a 50 años, pero las causas de este riesgo difirieron. Las poblaciones de P. ruthii en el Río Hiwassee tuvieron poblaciones iniciales más grandes, pero tasas de crecimiento significativamente menores, que las poblaciones en el Río Ocoee. Las únicas poblaciones con bajo riesgo de extinción pronosticado estaban en el Ocoee. Las tasas de crecimiento de las poblaciones en ambos ríos se redujeron significativamente durante períodos de bajo flujo en el río. Sólo encontramos evidencia marginal de la relación cuadrática entre el funcionamiento de la población y el flujo. Estos patrones son consistentes con la idea de que los bajos flujos afectan a P. ruthii debido al crecimiento de vegetación competitiva, pero aun no es claro el grado en que flujos muy grandes pueden reducir el crecimiento poblacional. Las simulaciones indicaron que las poblaciones son más sensibles a las tasas de crecimiento en años con bajo flujo en los ríos, pero pequeños cambios en la frecuencia de esos períodos no aumentaron el riesgo en la mayoría de las poblaciones. Consistentemente con los resultados de otros estudios, las estimaciones del riesgo de extinción mediante el método de difusión tienen amplios límites de confianza. Aun así, nuestros resultados aportaron varios conocimientos valiosos, incluyendo la necesidad de mayor monitoreo de las poblaciones en el Hiwassee y la importancia para el crecimiento poblacional de los años con bajo flujo. Nuestro trabajo ilustra el valor potencial de métodos sencillos de análisis de datos de conteo a pesar de los retos impuestos por la incertidumbre en las estimaciones del riesgo de extinción. [source]


    Robust Estimation and Outlier Detection for Overdispersed Multinomial Models of Count Data

    AMERICAN JOURNAL OF POLITICAL SCIENCE, Issue 2 2004
    Walter R. Mebane Jr.
    We develop a robust estimator,the hyperbolic tangent (tanh) estimator,for overdispersed multinomial regression models of count data. The tanh estimator provides accurate estimates and reliable inferences even when the specified model is not good for as much as half of the data. Seriously ill-fitted counts,outliers,are identified as part of the estimation. A Monte Carlo sampling experiment shows that the tanh estimator produces good results at practical sample sizes even when ten percent of the data are generated by a significantly different process. The experiment shows that, with contaminated data, estimation fails using four other estimators: the nonrobust maximum likelihood estimator, the additive logistic model and two SUR models. Using the tanh estimator to analyze data from Florida for the 2000 presidential election matches well-known features of the election that the other four estimators fail to capture. In an analysis of data from the 1993 Polish parliamentary election, the tanh estimator gives sharper inferences than does a previously proposed heteroskedastic SUR model. [source]


    A New Approach for Handling Longitudinal Count Data with Zero-Inflation and Overdispersion: Poisson Geometric Process Model

    BIOMETRICAL JOURNAL, Issue 4 2009
    Wai-Yin Wan
    Abstract For time series of count data, correlated measurements, clustering as well as excessive zeros occur simultaneously in biomedical applications. Ignoring such effects might contribute to misleading treatment outcomes. A generalized mixture Poisson geometric process (GMPGP) model and a zero-altered mixture Poisson geometric process (ZMPGP) model are developed from the geometric process model, which was originally developed for modelling positive continuous data and was extended to handle count data. These models are motivated by evaluating the trend development of new tumour counts for bladder cancer patients as well as by identifying useful covariates which affect the count level. The models are implemented using Bayesian method with Markov chain Monte Carlo (MCMC) algorithms and are assessed using deviance information criterion (DIC). [source]


    Hierarchical Bayesian Analysis of Correlated Zero-inflated Count Data

    BIOMETRICAL JOURNAL, Issue 6 2004
    Getachew A. Dagne
    Abstract This article presents two-component hierarchical Bayesian models which incorporate both overdispersion and excess zeros. The components may be resultants of some intervention (treatment) that changes the rare event generating process. The models are also expanded to take into account any heterogeneity that may exist in the data. Details of the model fitting, checking and selecting alternative models from a Bayesian perspective are also presented. The proposed methods are applied to count data on the assessment of an efficacy of pesticides in controlling the reproduction of whitefly. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Comparison of Hierarchical Bayesian Models for Overdispersed Count Data using DIC and Bayes' Factors

    BIOMETRICS, Issue 3 2009
    Russell B. Millar
    Summary When replicate count data are overdispersed, it is common practice to incorporate this extra-Poisson variability by including latent parameters at the observation level. For example, the negative binomial and Poisson-lognormal (PLN) models are obtained by using gamma and lognormal latent parameters, respectively. Several recent publications have employed the deviance information criterion (DIC) to choose between these two models, with the deviance defined using the Poisson likelihood that is obtained from conditioning on these latent parameters. The results herein show that this use of DIC is inappropriate. Instead, DIC was seen to perform well if calculated using likelihood that was marginalized at the group level by integrating out the observation-level latent parameters. This group-level marginalization is explicit in the case of the negative binomial, but requires numerical integration for the PLN model. Similarly, DIC performed well to judge whether zero inflation was required when calculated using the group-marginalized form of the zero-inflated likelihood. In the context of comparing multilevel hierarchical models, the top-level DIC was obtained using likelihood that was further marginalized by additional integration over the group-level latent parameters, and the marginal densities of the models were calculated for the purpose of providing Bayes' factors. The computational viability and interpretability of these different measures is considered. [source]


    Bayesian Prediction of Spatial Count Data Using Generalized Linear Mixed Models

    BIOMETRICS, Issue 2 2002
    Ole F. Christensen
    Summary. Spatial weed count data are modeled and predicted using a generalized linear mixed model combined with a Bayesian approach and Markov chain Monte Carlo. Informative priors for a data set with sparse sampling are elicited using a previously collected data set with extensive sampling. Furthermore, we demonstrate that so-called Langevin-Hastings updates are useful for efficient simulation of the posterior distributions, and we discuss computational issues concerning prediction. [source]


    Testing Trend for Count Data with Extra-Poisson Variability

    BIOMETRICS, Issue 2 2002
    Erni Tri Astuti
    Summary. Trend tests for monotone trend or umbrella trend (monotone upward changing to monotone downward or vise versa) in count data are proposed when the data exhibit extra-Poisson variability. The proposed tests, which are called the GS1 test and the GS2 test, are constructed by applying an orthonormal score vector to a generalized score test under an rth-order log-linear model. These tests are compared by simulation with the Cochran-Armitage test and the quasi-likelihood test of Piegorsch and Bailer (1997, Statastics for Enuiron, mental Biology and Toxicology). It is shown that the Cochran-Armitage test should not be used under the existence of extra-Poisson variability; that, for detecting monotone trend, the GS1 test is superior to the others; and that the GS2 test has high power to detect an umbrella response. [source]


    Fluctuations of Vanessa cardui butterfly abundance with El Niño and Pacific Decadal Oscillation climatic variables

    GLOBAL CHANGE BIOLOGY, Issue 5 2003
    ROBERT VANDENBOSCH
    Abstract Annual 4th of July Butterfly Count data spanning more than 20 years are examined to explore Vanessa cardui (Painted Lady) population fluctuations with ENSO (El Niño) and Pacific Decadal Oscillation (PDO) indices. California, Colorado and Nebraska censuses exhibit a strong positive correlation with the strong El Niño events of 1982,1983 and 1997,1998 and the weaker event of 1991,1992. Regression analysis shows the population fluctuations are strongly coupled to climate variations on both short (El Niño) and longer (Pacific Decadal Oscillation) time scales. Recognizing the sensitivity to these time scales is important for predicting longer-term global climate change effects. [source]


    Using Population Count Data to Assess the Effects of Changing River Flow on an Endangered Riparian Plant

    CONSERVATION BIOLOGY, Issue 4 2006
    DIANE M. THOMSON
    análisis de viabilidad poblacional; gestión ribereña; método de difusión; presas; riesgo de extinción Abstract:,Methods for using simple population count data to project extinction risk have been the focus of much recent theoretical work, but few researchers have used these approaches to address management questions. We analyzed 15 years of census data on the federally endangered endemic riparian plant Pityopsis ruthii (Small) with the diffusion approximation (DA). Our goals were to evaluate relative extinction risk among populations in two different watersheds (in Tennessee, U.S.A.) and potential effects of variation in managed river flow on population dynamics. Populations in both watersheds had high projected risks of extinction within 50 years, but the causes of this risk differed. Populations of P. ruthii on the Hiwassee River had higher initial population sizes but significantly lower average growth rates than those on the Ocoee River. The only populations with low predicted short-term extinction risk were on the Ocoee. Growth rates for populations on both rivers were significantly reduced during periods of lower river flow. We found only marginal evidence of a quadratic relationship between population performance and flow. These patterns are consistent with the idea that low flows affect P. ruthii due to growth of competing vegetation, but the degree to which very high flows may reduce population growth is still unclear. Simulations indicated that populations were most sensitive to growth rates in low-flow years, but small changes in the frequency of these periods did not strongly increase risk for most populations. Consistent with results of other studies, DA estimates of extinction risk had wide confidence limits. Still, our results yielded several valuable insights, including the need for greater monitoring of populations on the Hiwassee and the importance of low-flow years to population growth. Our work illustrates the potential value of simple methods for analyzing count data despite the challenges posed by uncertainty in estimates of extinction risk. Resumen:,Los métodos que utilizan datos de conteos simples de la población para proyectar el riesgo de extinción han sido el foco reciente de mucho trabajo teórico, pero pocos investigadores han utilizado estos métodos para responder preguntas de gestión. Analizamos 15 años de datos de censos de la planta ribereña, endémica y federalmente en peligro Pityopsis ruthii (Small) mediante el método de difusión. Nuestras metas fueron evaluar el riesgo de extinción de poblaciones en dos cuencas hidrológicas distintas y con dos efectos potenciales de la variación del flujo de agua sobre la dinámica de la población. Las poblaciones en ambas cuencas tenían alto riesgo de extinción proyectado a 50 años, pero las causas de este riesgo difirieron. Las poblaciones de P. ruthii en el Río Hiwassee tuvieron poblaciones iniciales más grandes, pero tasas de crecimiento significativamente menores, que las poblaciones en el Río Ocoee. Las únicas poblaciones con bajo riesgo de extinción pronosticado estaban en el Ocoee. Las tasas de crecimiento de las poblaciones en ambos ríos se redujeron significativamente durante períodos de bajo flujo en el río. Sólo encontramos evidencia marginal de la relación cuadrática entre el funcionamiento de la población y el flujo. Estos patrones son consistentes con la idea de que los bajos flujos afectan a P. ruthii debido al crecimiento de vegetación competitiva, pero aun no es claro el grado en que flujos muy grandes pueden reducir el crecimiento poblacional. Las simulaciones indicaron que las poblaciones son más sensibles a las tasas de crecimiento en años con bajo flujo en los ríos, pero pequeños cambios en la frecuencia de esos períodos no aumentaron el riesgo en la mayoría de las poblaciones. Consistentemente con los resultados de otros estudios, las estimaciones del riesgo de extinción mediante el método de difusión tienen amplios límites de confianza. Aun así, nuestros resultados aportaron varios conocimientos valiosos, incluyendo la necesidad de mayor monitoreo de las poblaciones en el Hiwassee y la importancia para el crecimiento poblacional de los años con bajo flujo. Nuestro trabajo ilustra el valor potencial de métodos sencillos de análisis de datos de conteo a pesar de los retos impuestos por la incertidumbre en las estimaciones del riesgo de extinción. [source]


    INAR(1) modeling of overdispersed count series with an environmental application

    ENVIRONMETRICS, Issue 4 2008
    Harry Pavlopoulos
    Abstract This paper is concerned with a novel version of the INAR(1) model, a non-linear auto-regressive Markov chain on ,, with innovations following a finite mixture distribution of Poisson laws. For , the stationary marginal probability distribution of the chain is overdispersed relative to a Poisson, thus making INAR(1) suitable for modeling time series of counts with arbitrary overdispersion. The one-step transition probability function of the chain is also a finite mixture, of m Poisson-Binomial laws, facilitating likelihood-based inference for model parameters. An explicit EM-algorithm is devised for inference by maximization of a conditional likelihood. Alternative options for inference are discussed along with criteria for selecting m. Integer-valued prediction (IP) is developed by a parametric bootstrap approach to ,coherent' forecasting, and a certain test statistic based on predictions is introduced for assessing performance of the fitted model. The proposed model is fitted to time series of counts of pixels where spatially averaged rain rate exceeds a given threshold level, illustrating its capabilities in challenging cases of highly overdispersed count data. Copyright © 2007 John Wiley & Sons, Ltd. [source]


    A Bayesian hierarchical model for over-dispersed count data: a case study for abundance of hake recruits

    ENVIRONMETRICS, Issue 1 2007
    Jorge M. Mendes
    Abstract In this paper, we introduce a Bayesian Hierarchical model to estimate the abundance of hake recruits, as well as to study their spatial distributional patterns in the Portuguese territorial waters. Main objective of the paper is to improve on traditional empirical methods based on sampling averages and variances by using probabilistic models that capture spatial dependence structures. Copyright © 2006 John Wiley & Sons, Ltd. [source]


    Beyond Mule Kicks: The Poisson Distribution in Geographical Analysis

    GEOGRAPHICAL ANALYSIS, Issue 2 2006
    Daniel A. Griffith
    The Poisson model, discovered nearly two centuries ago, is the basis for analyses of rare events. Its first applications included descriptions of deaths from mule kicks. More than half a century ago the Poisson model began being used in geographical analysis. Its initial descriptions of geographic distributions of points, disease maps, and spatial flows were accompanied by an assumption of independence. Today this unrealistic assumption is replaced by one allowing for the presence of spatial autocorrelation in georeferenced counts. Contemporary statistical theory has led to the creation of powerful Poisson-based modeling tools for geographically distributed count data. [source]


    The ,oestrogen hypothesis', where do we stand now?,

    INTERNATIONAL JOURNAL OF ANDROLOGY, Issue 1 2003
    Richard M. Sharpe
    Summary The original ,oestrogen hypothesis' postulated that the apparent increase in human male reproductive developmental disorders (testis cancer, cryptorchidism, hypospadias, low sperm counts) might have occurred because of increased oestrogen exposure of the human foetus/neonate; five potential routes of exposure were considered. This review revisits this hypothesis in the light of the data to have emerged since 1993. It addresses whether there is a secular increasing trend in the listed disorders and highlights the limitations of available data and how these are being addressed. It considers whether new data has emerged to support the suggestion that increased oestrogen exposure could cause these abnormalities and reviews new data on potential routes via which such increased exposure could have occurred. Secular trends: The disorders listed above are now considered to represent a syndrome of disorders (testicular dysgenesis syndrome, TDS) with a common origin in foetal life. Testicular cancer has increased in incidence in Caucasian men worldwide and lifetime risk is 0.3,0.8%. Secular trends in cryptorchidism are unclear but it is by far the commonest (2,4% at birth) congenital abnormality in either sex. Secular trends for hypospadias are not robust, although most studies suggest a progressive increase; registry data probably under-estimates incidence, but based on this data hypospadias is the second most common (0.3,0.7% at birth) congenital malformation. Retrospective analyses of sperm count data show a global downward trend but this is inconclusive , prospective studies using standardized methodology show significant differences between countries and very low sperm counts in the youngest cohort of men. For all disorders, other then testis cancer, standardized prospective studies are the best way forward and are in progress across Europe. Oestrogen effects: Evidence that foetal exposure to oestrogens can induce the above disorders has strengthened. New pathways via which such changes could be induced have been identified, including suppression of testosterone production by the foetal testis, suppression of androgen receptor expression and suppression of insulin-like factor-3 (InsL3) production by foetal Leydig cells. Other evidence suggests that the balance between androgen and oestrogen action may be important in induction of reproductive tract abnormalities. Oestrogen exposure: Although many new environmental oestrogens have been identified, their uniformly weak oestrogenicity excludes the possibility that they could induce the above disorders. However, emerging data implicates various environmental chemicals in being able to alter endogenous levels of androgens (certain phthalates) and oestrogens (polychlorinated biphenyls, polyhalogenated hydrocarbons), and the former have been shown to induce a similar collection of disorders to TDS. Other mechanisms via which increased fetal exposure to pregnancy oestrogens might occur (increasing trend in obesity, dietary changes) are also discussed. [source]


    Managing the wandering behaviour of people living in a residential aged care facility

    INTERNATIONAL JOURNAL OF EVIDENCE BASED HEALTHCARE, Issue 4 2007
    Brent Hodgkinson BSc MSc GradCertPubHealth GradCertHealthEcon
    Abstract Background, Wandering behaviour is frequently seen in older people with cognitive impairment. The prevalence of patients exhibiting wandering behaviour has been estimated to be 11.6% on traditional units and 52.7% on Alzheimer's units. Wandering is one of the core behavioural characteristics that impact on familial carers and is likely to influence the decision to place a family member in an aged care environment. Considering the possible risks associated with wandering behaviour, the successful identification and management of wandering is essential. Wandering is also a problem for caregivers in the institutionalised setting, in terms of containment, usually being addressed by securing the environment. There has been some research conducted to assist in the understanding and management of wandering behaviour; however, the findings have been diverse resulting in a level of confusion about the best approaches to take. Objectives, This review aims to present the best available evidence on the management of wandering in older adults who reside in an aged care facility (both high and low care). Search strategy, An extensive search of keywords contained in the title and abstract, and relevant MeSH headings and descriptor terms was performed on the following databases: MEDLINE, CINAHL, PsychINFO, AGELINE, Cochrane Library, Embase, APAIS Health, Current Contents, Dare, Dissertation Abstracts, Personal Communication, Social Science Index. Selection criteria, Papers were selected if they focused on the treatment of wandering in an institutional setting. Some studies were not specifically examining wanderers over the age of 65 years as per the protocol requirements, but were included as it was felt that their findings could be applied to this age group. Data collection and analysis, Study design and quality were tabulated and relative risks, odds ratios, mean differences and associated 95% confidence intervals were calculated from individual comparative studies containing count data where possible. All other data were presented in a narrative summary. Results, Searches identified one care protocol, two systematic reviews and 24 other studies that satisfied the inclusion criteria. The following recommendations are divided into four categories of interventions (environmental, technology and safety, physical/psychosocial, and caregiving support and education) with only Level 1, 2 or 3 evidence presented. Environmental modifications, Gridlines placed in front of doors or covering exit door doorknobs or panic bars may be effective at reducing exit-seeking behaviour (Level 3b). Technology and safety, Mobile locator devices may be effective at enabling quick location of wandering residents (Level 3c). Physical/psychosocial interventions, Implementation of a walking group or an exercise program may reduce the incidence of disruptive wandering behaviour (Level 3b). Use of air mat therapy may reduce wandering behaviour for at least 15 min post therapy (Level 2). Providing music sessions (and reading sessions) may keep residents from wandering during the period of the session (Level 3b). Caregiving support and education, There is no evidence to support any interventions. Conclusions, The majority of the available research for which the guidelines are based upon was derived from observational studies or expert opinion (Level of evidence 3 or 4). More rigorous research is required to demonstrate the efficacy of these recommendations. [source]


    Strategies to reduce medication errors with reference to older adults

    INTERNATIONAL JOURNAL OF EVIDENCE BASED HEALTHCARE, Issue 1 2006
    Brent Hodgkinson BSc (Hons) MSc GradCertPH GradCertEcon(Health)
    Abstract Background, In Australia, around 59% of the general population uses prescription medication with this number increasing to about 86% in those aged 65 and over and 83% of the population over 85 using two or more medications simultaneously. A recent report suggests that between 2% and 3% of all hospital admissions in Australia may be medication related with older Australians at higher risk because of higher levels of medicine intake and increased likelihood of being admitted to hospital. The most common medication errors encountered in hospitals in Australia are prescription/medication ordering errors, dispensing, administration and medication recording errors. Contributing factors to these errors have largely not been reported in the hospital environment. In the community, inappropriate drugs, prescribing errors, administration errors, and inappropriate dose errors are most common. Objectives, To present the best available evidence for strategies to prevent or reduce the incidence of medication errors associated with the prescribing, dispensing and administration of medicines in the older persons in the acute, subacute and residential care settings, with specific attention to persons aged 65 years and over. Search strategy, Bibliographic databases PubMed, Embase, Current contents, The Cochrane Library and others were searched from 1986 to present along with existing health technology websites. The reference lists of included studies and reviews were searched for any additional literature. Selection criteria, Systematic reviews, randomised controlled trials and other research methods such as non-randomised controlled trials, longitudinal studies, cohort or case,control studies, or descriptive studies that evaluate strategies to identify and manage medication incidents. Those people who are involved in the prescribing, dispensing or administering of medication to the older persons (aged 65 years and older) in the acute, subacute or residential care settings were included. Where these studies were limited, evidence available on the general patient population was used. Data collection and analysis, Study design and quality were tabulated and relative risks, odds ratios, mean differences and associated 95% confidence intervals were calculated from individual comparative studies containing count data where possible. All other data were presented in a narrative summary. Results, Strategies that have some evidence for reducing medication incidents are: ,,computerised physician ordering entry systems combined with clinical decision support systems; ,,individual medication supply systems when compared with other dispensing systems such as ward stock approaches; ,,use of clinical pharmacists in the inpatient setting; ,,checking of medication orders by two nurses before dispensing medication; ,,a Medication Administration Review and Safety committee; and ,,providing bedside glucose monitors and educating nurses on importance of timely insulin administration. In general, the evidence for the effectiveness of intervention strategies to reduce the incidence of medication errors is weak and high-quality controlled trials are needed in all areas of medication prescription and delivery. [source]


    Effectiveness of topical skin care provided in aged care facilities

    INTERNATIONAL JOURNAL OF EVIDENCE BASED HEALTHCARE, Issue 4 2005
    Brent Hodgkinson MSc GradCertPH GradCertEcon(Health)
    Executive summary Background, The 2001 Australian census revealed that adults aged 65 years and over constituted 12.6% of the population, up from 12.1% in 1996. It is projected that this figure will rise to 21% or 5.1 million Australians by 2031. In 1998, 6% (134 000) of adults in Australia aged 65 years and over were residing in nursing homes or hostels and this number is also expected to rise. As skin ages, there is a decreased turnover and replacement of epidermal skin cells, a thinning subcutaneous fat layer and a reduced production of protective oils. These changes can affect the normal functions of the skin such as its role as a barrier to irritants and pathogens, temperature and water regulation. Generally, placement in a long-term care facility indicates an inability of the older person to perform all of the activities of daily living such as skin care. Therefore, skin care management protocols should be available to reduce the likelihood of skin irritation and breakdown and ultimately promote comfort of the older person. Objectives, The objective of this review was to determine the best available evidence for the effectiveness and safety of topical skin care regimens for older adults residing in long-term aged care facilities. The primary outcome was the incidence of adverse skin conditions with patient satisfaction considered as a secondary outcome. Search strategy, A literature search was performed using the following databases: PubMed (NLM) (1966,4/2003), Embase (1966,4/2003), CINAHL (1966,4/2003), Current Contents (1993,4/2003), Cochrane Library (1966,2/2003), Web of Science (1995,12/2002), Science Citation Index Expanded and ProceedingsFirst (1993,12/2002). Health Technology Assessment websites were also searched. No language restrictions were applied. Selection criteria, Systematic reviews of randomised controlled trials, randomised and non-randomised controlled trials evaluating any non-medical intervention or program that aimed to maintain or improve the integrity of skin in older adults were considered for inclusion. Participants were 65 years of age or over and residing in an aged care facility, hospital or long-term care in the community. Studies were excluded if they evaluated pressure-relieving techniques for the prevention of skin breakdown. Data collection and analysis, Two independent reviewers assessed study eligibility for inclusion. Study design and quality were tabulated and relative risks, odds ratios, mean differences and associated 95% confidence intervals were calculated from individual comparative studies containing count data. Results, The resulting evidence of the effectiveness of topical skin care interventions was variable and dependent upon the skin condition outcome being assessed. The strongest evidence for maintenance of skin condition in incontinent patients found that disposable bodyworn incontinence protection reduced the odds of deterioration of skin condition compared with non-disposable bodyworns. The best evidence for non-pressure relieving topical skin care interventions on pressure sore formation found the no-rinse cleanser Clinisan to be more effective than soap and water at maintaining healthy skin (no ulcers) in elderly incontinent patients in long-term care. The quality of studies examining the effectiveness of topical skin care interventions on the incidence of skin tears was very poor and inconclusive. Topical skin care for prevention of dermatitis found that Sudocrem could reduce the redness of skin compared with zinc cream if applied regularly after each pad change, but not the number of lesions. Topical skin care on dry skin found the Bag Bath/Travel Bath no-rinse skin care cleanser to be more effective at preventing overall skin dryness and most specifically flaking and scaling when compared with the traditional soap and water washing method in residents of a long-term care facility. Information on the safety of topical skin care interventions is lacking. Therefore, because of the lack of evidence, no recommendation on the safety on any intervention included in this review can be made. [source]


    Evaluating the power of monitoring plot designs for detecting long-term trends in the numbers of common guillemots

    JOURNAL OF APPLIED ECOLOGY, Issue 3 2006
    MICHELLE SIMS
    Summary 1In recent years concerns have been raised regarding the status of the common guillemot Uria aalge in the UK. Numbers have declined in several regions, highlighting the need for continued monitoring of this internationally important population. However, the extent to which the current monitoring scheme is capable of detecting declines and options for improving efficiency has received little attention. 2We investigated the power of different monitoring design options for detecting long-term trends in abundance at a colony of guillemots. The ability to detect trends in abundance was reduced by the large temporal and spatial variability in colony attendance. Taking a linear mixed model approach, we obtained details on the sources and sizes of the variance components using count data collected from monitoring plots on the Isle of May, Scotland, and assessed how best to allocate sampling effort in the light of the count variability structure. 3Our results indicated that trend detection will be improved by counting birds in more plots rather than by increasing the number of counts at existing plots. 4The revisit pattern of counts at the monitoring plots during the seasonal counting period had little effect on trend detection power. However, given the practical issues associated with counting guillemots, alternative revisit patterns to the current approach are preferred. 5For a fixed number of visits per plot, power is strongly influenced by the choice of revisit design if the day-to-day variation in colony attendance is increased. 6Synthesis and applications. Aspects of the UK seabird monitoring scheme can be improved. Changes to the allocation of sampling effort and the plot-revisit pattern will improve both the statistical power to detect long-term trends and the efficiency of conducting the survey. We stress the importance of considering the structure and magnitude of the count variation in a power analysis because judicious design decisions depend on the relative magnitude of these variance components. [source]


    A novel in vitro flat-bed perfusion biofilm model for determining the potential antimicrobial efficacy of topical wound treatments

    JOURNAL OF APPLIED MICROBIOLOGY, Issue 6 2009
    R.M.S. Thorn
    Abstract Aims:, To develop an in vitro flat-bed perfusion biofilm model that could be used to determine the antimicrobial efficacy of topically applied treatments. Methods and Results:,Pseudomonas aeruginosa and Staphylococcus aureus biofilms were grown within continuously perfused cellulose matrices. Enumeration of the biofilm density and eluate was performed at various sampling times, enabling determination of the biofilm growth rate. Two antimicrobial wound dressings were applied to the surface of mature biofilms and periodically sampled. To enable real-time imaging of biofilm growth and potential antimicrobial kinetics, a bioluminescent Ps. aeruginosa biofilm was monitored using low-light photometry. Target species produced reproducible steady-state biofilms at a density of c. 107 per biofilm support matrix, after 24-h perfusion. Test dressings elicited significant antimicrobial effects, producing differing kill kinetic profiles. There was a good correlation between photon and viable count data. Conclusions:, The model enables determination of the antimicrobial profile of topically applied treatments against target species biofilms, accurately differentiating bactericidal from bacteriostatic effects. Moreover, these effects could be monitored in real time using bioluminescence. Significance and Impact of the Study:, This is the first in vitro biofilm model which can assess the antimicrobial potential of topical therapies in a dynamic growth environment. [source]


    Modelling of Campylobacter survival in frozen chicken meat

    JOURNAL OF APPLIED MICROBIOLOGY, Issue 3 2007
    M. Ritz
    Abstract Aims:, To model the survival kinetics of Campylobacter jejuni on frozen chicken meat. Methods and Results:, Three different types of chicken meat surface (skin, skinned muscle and cut muscle) were inoculated with stationary phase cells of C. jejuni (8 log10 CFU cm,2) and frozen for 5 weeks at ,20°C. Bacterial numbers were determined weekly using two different methods of enumeration to quantify uninjured and injured cells. Analysis of variance of the results showed that the type of chicken surface and the method used to enumerate surviving cells were the most significant sources of variations in the numbers recovered (P < 0·0001), much more than the freezing time. To identify an appropriate model for the description of effects of freezing on survival over time, several models were fitted to the count data. Decay was found to be nonlinear. In general, survival was least on skin, better on skinned muscle and best on cut muscle. After 2 weeks, additional inactivation by freezing appeared to be negligible. Conclusion:, Because of the variability of survival it was not possible to fit and select a general model useful for all the different surfaces types. Significance and Impact of the Study:, The injured state of the cells leads to variability and the underestimation of bacterial survival. This is an essential factor for the assessment of Campylobacter -associated risk. [source]


    Cross-contamination of carcasses and equipment during pork processing

    JOURNAL OF APPLIED MICROBIOLOGY, Issue 1 2002
    K. Warriner
    Aims: ,The cross-contamination events within a commercial pork processing line were examined by a combination of ERIC-PCR DNA fingerprinting of Escherichia coli and plate counts. Methods and Results: ,Sponge sampling of environmental surfaces and carcasses was performed over an 8-h processing period. Prior to the start of processing the scraper and dry polisher blades were found to harbour substantial Enterobacteriaceae and Escherichia coli populations. From plate count data the key cross-contamination site for the transfer of bacteria between carcasses occurred during evisceration. However, DNA fingerprints of representative E. coli isolates identified that genotypes initially present on the scraper/dry polisher became distributed on wet polisher blades, band-saw and butcher's hands despite a singeing step being performed post dry polishing. A high proportion of E. coli on post-eviscerated carcasses could be traced to down-stream (pre-singe) environmental contact surfaces. Conclusions: ,DNA fingerprinting has demonstrated that E. coli and potential enteric pathogens can be transferred between pork carcasses throughout the processing line. In this respect scalding and singeing cannot be relied upon to control cross-contamination of enteric bacteria between carcasses. Significance and Impact of the Study: ,Sole reliance on indicator organism counts to identify cross-contamination events as currently advocated is limited. [source]


    The diversity and abundance of North American butterflies vary with habitat disturbance and geography

    JOURNAL OF BIOGEOGRAPHY, Issue 4 2000
    Scott D. Kocher
    Abstract Aim We used data from the annual Fourth of July Butterfly Count for the years 1989,97 to examine patterns of species richness and total butterfly abundance across North America and within topographically diverse and disturbed landscapes. Location We analysed counts from 514 different locations in North America. The counts represent all areas of the USA and southern Canada, with a few Mexican sites as well, although most counts were in the eastern USA. Methods First, we standardized published count data according to the effort expended per count (total party-hours). Using regression analysis and analysis of variance, we then examined the impact of latitude, longitude, topographical relief, habitat disturbance and different climatic measures on the species richness and total abundance of butterflies per count. We also examined the abundance of exotic species in disturbed landscapes. Results Our analyses suggest that: (1) species richness is highest at low latitudes and near Rocky Mountain longitudes; (2) the total abundance of individuals is highest in northern US latitudes and Great Plains longitudes; (3) species richness but not total abundance increases with greater topographical relief; (4) species richness and diversity indices are lower in more disturbed habitats; and (5) the abundance of the introduced Pieris rapae (L.) is greater in more disturbed habitats. Main conclusions Different factors control the abundance and species richness of North American butterflies. Along with geographical location, habitat disturbance and topographical variability affect species richness. Our analysis also shows the value of broad-based monitoring regimes, such as the North American Fourth of July Butterfly Count. [source]


    A comparison of different pre-treatment procedures for reducing heteroscedasticity and other irrelevant features in data prior to modelling of benthic count profiles

    JOURNAL OF CHEMOMETRICS, Issue 7-9 2007
    Geir Rune Flåten
    Abstract Challenges related to quantifying environmental disturbance biologically from benthic count profiles by using the Community Disturbance Index (CDI) approach are assessed. A pre-treatment framework incorporating removal of irrelevant features, scaling and converting transformations is proposed. Within this framework the characteristics of benthic count data are discussed and possible consequences for the CDI calculations are shown. It is established that the benthic count data need to be corrected for heteroscedasticity while scaling is found to be unnecessary for the CDI calculations. Copyright © 2007 John Wiley & Sons, Ltd. [source]


    Detection, survival rates and dynamics of a cryptic plant, Asclepias meadii: applications of mark-recapture models to long-term monitoring studies

    JOURNAL OF ECOLOGY, Issue 2 2009
    Helen M. Alexander
    Summary 1Analysis of population trajectories is central to assessing risk in populations of conservation concern. In animal studies, researchers realize that probabilities of detection of individuals are often less than one. Plants can also escape detection due to dormancy, herbivory, or observer error, but such information is rarely incorporated into population studies. 2We monitored a population of Asclepias meadii, a rare long-lived prairie perennial. Despite standardized methods, numbers of observed plants fluctuated greatly from 1992 to 2006. Individual plants often had periods of 1,5 years between initial and final sighting when no stems were found. To determine the actual population trajectories, we estimated rates of survival and population growth using mark-recapture models. We also estimated initial and resighting probabilities of detection. In 2007, we repeated surveys to identify reasons for low detection probabilities. 3We estimated 95% annual survival and a population growth rate of 1.023. Probabilities of initial detection were low (typically from 0.120 to 0.311 depending on prairie burn treatment), whereas average probability of detection for marked plants was 0.728. 4Comparisons of survival estimates from 15- and 8-year data sets revealed that survival estimates decline in the final years of a multi-year period, probably due to heterogeneity in encounter histories. 5By conducting three different surveys in 2007, we found that both herbivory over a multiple-week period and observer error contributed substantially to gaps in detection. 6Synthesis. Probabilities of detection that are less than one complicate interpretation of population dynamics, whether of mobile animals or inconspicuous plants. Our work illustrates three general points that could apply to many plant population studies: (i) mark-recapture models may provide insights on vital rates and population trajectories despite the extreme variability in count data that can arise because of low detectability, (ii) probabilities of initial detection can be quantified and can be considerably less than probabilities of resighting, and (iii) repeated surveys can help researchers determine the degree to which dormancy, herbivory, or observer error contribute to low probabilities of detection. Consideration of these points can improve the design and analysis of monitoring programs. [source]


    Post-transfusion white cell count in the sick preterm neonate

    JOURNAL OF PAEDIATRICS AND CHILD HEALTH, Issue 1 2001
    IMR Wright
    Objective: A previous report demonstrated post-transfusion leucocytosis as a potential confounding factor in the diagnosis of sepsis in critically ill adult patients. In We wished to establish if the same phenomenon occurred in the sick preterm neonate and whether this significantly altered the indices considered for potential neonatal infection. Methodology: Transfusion and full blood count data in a level 3 neonatal intensive care unit were prospectively recorded for 3 months. Results: One hundred and fourteen transfusion events were recorded from 37 infants. Median white blood cell count increased 0.9 × 109/L (confidence interval (CI) 0.4,2.4) in the first 8 h following transfusion (P = 0.032). Median neutrophil count increased by 0.4 × 109/L (CI 0.1,1.7) in the same 8 h (P = 0.05). Median neutrophil left shift decreased 1.2% (CI 1.1,5.8%) over the 24 h post-transfusion. No change in band count was observed. Conclusions: A mild post-transfusion white cell increase occurs in sick neonates. Because of the magnitude of effect, it is unlikely that this interesting physiological response would interfere with the diagnosis of sepsis in this population. [source]


    Number of Accidents or Number of Claims?

    JOURNAL OF RISK AND INSURANCE, Issue 4 2009
    An Approach with Zero-Inflated Poisson Models for Panel Data
    The,hunger for bonus,is a well-known phenomenon in insurance, meaning that the insured does not report all of his accidents to save bonus on his next year's premium. In this article, we assume that the number of accidents is based on a Poisson distribution but that the number of claims is generated by censorship of this Poisson distribution. Then, we present new models for panel count data based on the zero-inflated Poisson distribution. From the claims distributions, we propose an approximation of the accident distribution, which can provide insight into the behavior of insureds. A numerical illustration based on the reported claims of a Spanish insurance company is included to support this discussion. [source]


    Analysis of publications and citations from a geophysics research institute

    JOURNAL OF THE AMERICAN SOCIETY FOR INFORMATION SCIENCE AND TECHNOLOGY, Issue 9 2001
    Cliff Frohlich
    We here perform an analysis of all 1128 publications produced by scientists during their employment at the University of Texas Institute for Geophysics, a geophysical research laboratory founded in 1972 that currently employs 23 Ph.D.-level scientists. We thus assess research performance using as bibliometric indicators such statistics as publications per year, citations per paper, and cited half-lives. To characterize the research style of individual scientists and to obtain insight into the origin of certain publication-counting discrepancies, we classified the 1128 publications into four categories that differed significantly with respect to statistics such as lifetime citation rates, fraction of papers never-cited after 10 years, and cited half-life. The categories were: mainstream (prestige journal) publications,32.6 lifetime cit/pap, 2.4% never cited, and 6.9 year half-life; archival (other refereed),12.0 lifetime cit/pap. 21.5% never cited, and 9.5 years half-life; articles published as proceedings of conferences,5.4 lifetime cit/pap, 26.6% never cited, and 5.4 years half-life; and "other" publications (news articles, book reviews, etc.),4.2 lifetime cit/pap, 57.1% never cited, and 1.9 years half-life. Because determining cited half-lives is highly similar to a well-studied phenomenon in earthquake seismology, which was familiar to us, we thoroughly evaluate five different methods for determining the cited half-life and discuss the robustness and limitations of the various methods. Unfortunately, even when data are numerous the various methods often obtain very different values for the half-life. Our preferred method determines half-life from the ratio of citations appearing in back-to-back 5-year periods. We also evaluate the reliability of the citation count data used for these kinds of analysis and conclude that citation count data are often imprecise. All observations suggest that reported differences in cited half-lives must be quite large to be significant. [source]


    A Bayesian model for longitudinal count data with non-ignorable dropout

    JOURNAL OF THE ROYAL STATISTICAL SOCIETY: SERIES C (APPLIED STATISTICS), Issue 5 2008
    Niko A. Kaciroti
    Summary., Asthma is an important chronic disease of childhood. An intervention programme for managing asthma was designed on principles of self-regulation and was evaluated by a randomized longitudinal study. The study focused on several outcomes, and, typically, missing data remained a pervasive problem. We develop a pattern,mixture model to evaluate the outcome of intervention on the number of hospitalizations with non-ignorable dropouts. Pattern,mixture models are not generally identifiable as no data may be available to estimate a number of model parameters. Sensitivity analyses are performed by imposing structures on the unidentified parameters. We propose a parameterization which permits sensitivity analyses on clustered longitudinal count data that have missing values due to non-ignorable missing data mechanisms. This parameterization is expressed as ratios between event rates across missing data patterns and the observed data pattern and thus measures departures from an ignorable missing data mechanism. Sensitivity analyses are performed within a Bayesian framework by averaging over different prior distributions on the event ratios. This model has the advantage of providing an intuitive and flexible framework for incorporating the uncertainty of the missing data mechanism in the final analysis. [source]


    Bayesian mixture models for complex high dimensional count data in phage display experiments

    JOURNAL OF THE ROYAL STATISTICAL SOCIETY: SERIES C (APPLIED STATISTICS), Issue 2 2007
    Yuan Ji
    Summary., Phage display is a biological process that is used to screen random peptide libraries for ligands that bind to a target of interest with high affinity. On the basis of a count data set from an innovative multistage phage display experiment, we propose a class of Bayesian mixture models to cluster peptide counts into three groups that exhibit different display patterns across stages. Among the three groups, the investigators are particularly interested in that with an ascending display pattern in the counts, which implies that the peptides are likely to bind to the target with strong affinity. We apply a Bayesian false discovery rate approach to identify the peptides with the strongest affinity within the group. A list of peptides is obtained, among which important ones with meaningful functions are further validated by biologists. To examine the performance of the Bayesian model, we conduct a simulation study and obtain desirable results. [source]


    Estimation of origin,destination trip rates in Leicester

    JOURNAL OF THE ROYAL STATISTICAL SOCIETY: SERIES C (APPLIED STATISTICS), Issue 4 2001
    Martin L. Hazelton
    The road system in region RA of Leicester has vehicle detectors embedded in many of the network's road links. Vehicle counts from these detectors can provide transportation researchers with a rich source of data. However, for many projects it is necessary for researchers to have an estimate of origin-to-destination vehicle flow rates. Obtaining such estimates from data observed on individual road links is a non-trivial statistical problem, made more difficult in the present context by non-negligible measurement errors in the vehicle counts collected. The paper uses road link traffic count data from April 1994 to estimate the origin,destination flow rates for region RA. A model for the error prone traffic counts is developed, but the resulting likelihood is not available in closed form. Nevertheless, it can be smoothly approximated by using Monte Carlo integration. The approximate likelihood is combined with prior information from a May 1991 survey in a Bayesian framework. The posterior is explored using the Hastings,Metropolis algorithm, since its normalizing constant is not available. Preliminary findings suggest that the data are overdispersed according to the original model. Results for a revised model indicate that a degree of overdispersion exists, but that the estimates of origin,destination flow rates are quite insensitive to the change in model specification. [source]