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At least 595 records · Page 33Linked to original sources
PubMed1991

Social deprivation and rates of treated mental disorder. Developing statistical models to predict psychiatric service utilisation.

A review of the literature shows that there are strong associations of treated prevalence rates of psychiatric disorder with social class, sex, marital status, ethnic group and living alone; and moderate associations with living in inner-city areas and a high degree of residential mobility. The Jarman-8 index of social deprivation correlates with psychiatric admission rates for patients aged less than 65 years (R2 = 0.38). Individual census variables can themselves account for up to 0.71 of the variance in the admission rates, while combined in a stepwise multiple regression the census variables will account for over 0.95 of this variation. Multiple regression models using individual census variables and derived indices should be applied next on a wider geographical basis, and to narrower age, sex and diagnosis-specific psychiatric morbidity rates.

Adolescent↗
PubMed2004

A spatial statistical model for landscape genetics.

Landscape genetics is a new discipline that aims to provide information on how landscape and environmental features influence population genetic structure. The first key step of landscape genetics is the spatial detection and location of genetic discontinuities between populations. However, efficient methods for achieving this task are lacking. In this article, we first clarify what is conceptually involved in the spatial modeling of genetic data. Then we describe a Bayesian model implemented in a Markov chain Monte Carlo scheme that allows inference of the location of such genetic discontinuities from individual geo-referenced multilocus genotypes, without a priori knowledge on populational units and limits. In this method, the global set of sampled individuals is modeled as a spatial mixture of panmictic populations, and the spatial organization of populations is modeled through the colored Voronoi tessellation. In addition to spatially locating genetic discontinuities, the method quantifies the amount of spatial dependence in the data set, estimates the number of populations in the studied area, assigns individuals to their population of origin, and detects individual migrants between populations, while taking into account uncertainty on the location of sampled individuals. The performance of the method is evaluated through the analysis of simulated data sets. Results show good performances for standard data sets (e.g., 100 individuals genotyped at 10 loci with 10 alleles per locus), with high but also low levels of population differentiation (e.g., FST<0.05). The method is then applied to a set of 88 individuals of wolverines (Gulo gulo) sampled in the northwestern United States and genotyped at 10 microsatellites.

Animals↗
PubMed2006

Spatio-temporal statistical models for river monitoring networks.

When introducing new wastewater treatment plants (WWTP), investors and policy makers often want to know if there indeed is a beneficial effect of the installation of a WWTP on the river water quality. Such an effect can be established in time as well as in space. Since both temporal and spatial components affect the output of a monitoring network, their dependence structure has to be modelled. River water quality data typically come from a river monitoring network for which the spatial dependence structure is unidirectional. Thus the traditional spatio-temporal models are not appropriate, as they cannot take advantage of this directional information. In this paper, a state-space model is presented in which the spatial dependence of the state variable is represented by a directed acyclic graph, and the temporal dependence by a first-order autoregressive process. The state-space model is extended with a linear model for the mean to estimate the effect of the activation of a WWTP on the dissolved oxygen concentration downstream.

Data Collection↗
PubMed1999

Variance components and breeding values for growth traits from different statistical models.

Estimates of genetic parameters resulting from various analytical models for birth weight (BWT, n = 4,155), 205-d weight (WWT, n = 3,884), and 365-d weight (YWT, n = 3,476) were compared. Data consisted of records for Line 1 Hereford cattle selected for postweaning growth from 1934 to 1989 at ARS-USDA, Miles City, MT. Twelve models were compared. Model 1 included fixed effects of year, sex, age of dam; covariates for birth day and inbreeding coefficients of animal and of dam; and random animal genetic and residual effects. Model 2 was the same as Model 1 but ignored inbreeding coefficients. Model 3 was the same as Model 1 and included random maternal genetic effects with covariance between direct and maternal genetic effects, and maternal permanent environmental effects. Model 4 was the same as Model 3 but ignored inbreeding. Model 5 was the same as Model 1 but with a random sire effect instead of animal genetic effect. Model 6 was the same as Model 5 but ignored inbreeding. Model 7 was a sire model that considered relationships among males. Model 8 was a sire model, assuming sires to be unrelated, but with dam effects as uncorrelated random effects to account for maternal effects. Model 9 was a sire and dam model but with relationships to account for direct and maternal genetic effects; dams also were included as uncorrelated random effects to account for maternal permanent environmental effects. Model 10 was a sire model with maternal grandsire and dam effects all as uncorrelated random effects. Model 11 was a sire and maternal grandsire model, with dams as uncorrelated random effects but with sires and maternal grandsires assumed to be related using male relationships. Model 12 was the same as Model 11 but with all pedigree relationships from the full animal model for sires and maternal grandsires. Rankings on predictions of breeding values were the same regardless of whether inbreeding coefficients for animal and dam were included in the models. Heritability estimates were similar regardless of whether inbreeding effects were in the model. Models 3 and 9 best fit the data for estimation of variances and covariances for direct, maternal genetic, and permanent environmental effects. Other models resulted in changes in ranking for predicted breeding values and for estimates of direct and maternal heritability. Heritability estimates of direct effects were smallest with sire and sire-maternal grandsire models.

Animals↗
PubMed1979

Timing and duration effects in residence histories and other longitudinal data: Part 1. Stochastic and statistical models; Part 2. Studies of duration effects in Norway, 1965-1971.

The author describes an attempt to fit stochastic models to individual life histories. "In particular, [he] is concerned with the application of semi-Markov processes to the study of the timing of moves and duration of residence effects in the migration histories of Norwegian men over the period 1965-1971." In the second part of the article, the results of 11 studies using data on Norwegian men are presented

Demography↗
PubMed2004

[Circadian rhythm variations of intraocular pressure and therapeutic decisions: interpretation of clinical trial results based on a statistical model].

Therapeutic decisions (treatment initiation, continuation, change, combination, etc.) based on intraocular pressure (IOP) monitoring require knowledge of both circadian IOP fluctuations and the pharmacological circadian rhythm of the active ingredients. A simple model was applied to data from two clinical trials to estimate the consequences of circadian IOP fluctuations on (1) ocular hypertension diagnosis, (2) therapeutic adjustments, and (3) the daily cumulative effect of marginally low therapeutic differences. A grid for clinical interpretation of the average IOP differences is presented. The probability of an IOP that exceeds the target value for the diagnosis or therapy varied to a large extent throughout the day. IOP was higher in the morning than in the evening. The IOP variance (measured by standard deviation) was an important factor in decision-making, regardless of the IOP value itself. Regular IOP monitoring over the entire day allowed minimization of the time spent above a target value. IOP differences that seemed low when expressed in average values in therapeutic trials could have clinically significant consequences in the practitioner's decisions. The data presented suggest that ocular hypertension diagnosis and therapeutic decisions should be made early in the morning, at least for most patients. In any case, the time of the measurement should be considered in the therapeutic approach.

Biotransformation↗
PubMed2005

[Correlation of intersubspecific hybrid rice spikelet fertilization rate with temperature and related statistic model].

Using four types of rice, i. e., indica-japonica hybrid, intermediate hybrid, indica and japonica cultivars as test materials, this paper studied the sensitivity of intersubspecific hybrid rice to climatic factors, and the correlations between spikelet fertilization rate (SFR) and daily meteorological factors during 2000 and 2001. The results showed that the SFR of intersubspecific hybrids was lower than that of indica and japonica cultivars. Among eleven meteorological factors, temperature was the key factor, and the mean temperature within five or seven days around panicle flower blooming affected the SFR significantly. A comprehensive model of SFR-temperature was established, with which, the fittest temperature and safe temperature for fertilization of intersubspecific hybrids was estimated to be 28.2 - 29.3 degrees C and 23.4 - 24.3 degrees C, 2.2 degrees C and 1.5 degrees C higher than those of indica and japonica cultivars, respectively. It was suggested that the safe heading date for planting intersubspecific hybrid should be moved up to the last ten-day of September to the first ten-day of October in southern China, the first ten-day of September in middle and lower reaches of Yangtze River Valley, and the last ten-day of August to the first ten-day of September in rice planting area between Yangtze and Huai River.

Chromosomes, Plant↗
PubMed1977

Computer study of thyroid diseases. III. Statistical models.

A binary-variable multiple-regression model is proposed for the computer diagnosis of thyroid disease. The procedure employs a multiple-regression technique in which each variable is assigned a value of either unity or zero. Unlike other current approaches, the proposed model uses only information about the patients themselves; no prior knowledge of the incidence of the disease in the population under study is required. The model was applied to data on 906 patients with suspected thyroid disorders referred to endocrine clinics in Israel. On the basis of simple physical findings and clinical signs and symptoms, the correct diagnosis was obtained in 95% of the cases for males and in 85% for females.

Diagnosis, Computer-Assisted↗
PubMedDate not supplied

[A two-dimensional statistical model of the otolith].

A model of the otolith as a system with distributed parameters in which the otolith is described by a two-dimensional elastic plate fixed at its sides is presented. The behavior of the model in response to centrifugal and gravitational forces is discussed. Comparison of this model with experimental data yields the value of Young's module of the otolith membrane equal to 10(2)-10(3) dyne/cm2. It is shown that deformations of different compartments of the otolith are dissimilar even for a homogeneous otolith membrane, depending on its configuration and orientation relative to the force vector. It is concluded that intralabyrinthine pressure may be the cause of original nonhomogeneous deformation of hairs in receptor cells at rest.

Gravitation↗
PubMed1986

Statistical models for predicting Edgerton-Danhauer NST scores from pure-tone thresholds.

Pure-tone thresholds (PTTs) and phonemic-scored responses to the Edgerton and Danhauer (1979) Nonsense Syllable Test (NST) at 25, 35, 45, and 55 db SL re each S's SRT, were taken from 97 Ss of 4 earlier studies of Danhauer and colleagues. All studies had used the same stimuli and procedures. Among the 97 Ss were heterogeneous subpopulations of normally-hearing and sensorineural hearing-impaired Ss, aged 6-81 yrs. PTTs at octaves from .25-8 kc/s, singly and in various weighted combinations, were explored by step-wise multiple linear regression analyses for the best equation to predict an individual's NST score at each SL. Included were the two weighted PTT averages (over .5, 1, and 2 kc/s) proposed by Butts, Schoney and Ruth (Asha, 1984, 26, 64). PTT2 kc/s was the single most predictive datum. The most predictive equation at one NST SL was not necessarily the best at another SL. At each NST SL, the most predictive equation was always one or other of the equations of Butts et al, and at the higher levels the best equations incorporated in addition certain weighted PTTs at .5 and 1 kc/s. The results indicated that it is possible to predict a S's NST scores from PTTs with reasonable accuracy: from 86-91% of Ss' NST scores were predicted within +/- 10%. Further validation and refinement of these models on larger and different subject samples may result in equations predicting NST scores from PTTs with those difficult-to-test patients in whom speech recognition capacity cannot well be tested directly.

Acoustic Stimulation↗
PubMed1986

[Tissue basophils in thermal damage to the skin in an experiment (morphometric analysis and statistical modelling)].

By means of quantitative morphological analysis tissue basophils (TB) (mast cells) in the derm and in the subcutaneous loose connective tissue have been studied at various degree of thermal lesion of the skin. Average diameter, amount of the cells per 0.1 mm2 of the slice area and distance between them serve as criteria for estimation of the TB functional activity. Certain differences have been revealed in the TB state at a weak and severe thermal lesion of the skin. At a threshold thermal action, metabolic processes in the TB become active. Burns of the skin of the II and IIIa degree result in an increased discharge of the granular component from cytoplasm and often in death of the cells. By means of multiple linear regression equations certain dependence of the degree of the thermal skin lesion on the state of the TB population in various dermal layers and in the subcutaneous loose connective tissue is stated.

Animals↗
PubMed1985

A statistical model for the study of self-fertilization in plants.

A model is proposed for the study of plant breeding where the self-fertilization rate is of importance. The model can be used to provide convenient maximum likelihood estimation of the self-fertilization rate and allelic frequencies in a parental population and its pollen pool. The self-fertilization rate can also be allowed to vary with genotype or other characteristics of a plant. A simple example illustrates the methodology.

Biometry↗