Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Binomial Distribution”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,495 records · Page 83Linked to original sources
PubMedDate not supplied

[Retrospective analysis of nursing records at a specialized unit].

This is a retrospective longitudinal study conducted in a Specialized Unit in the interior of Brazil. It aimed at verifying differences in nursing records with regard to how to document the care provided to patients in three periods related to the implementation of the Nursing process. Data were collected from 20% of the records of patients aged over 15 years who were randomly selected according to proportional distribution. Such data were fully transcribed in an instrument constructed for this purpose and classified according to the proposals of the referential. The Binomial Test was used for analysis with a significance level of 0.05%. The results showed a tendency to improvement of the records as to writing intellection and complete description of the signs/symptoms in the second period. It was concluded that there was a difference between the initial and the pre-implementation periods, which expresses the need to review the way the Nursing Process must be developed as a responsibility of the whole nursing team.

Hospital Units↗
PubMed1983

Statistical analysis and sample-size determinations for mutagenicity experiments with binomial responses.

Two statistical analyses are studied for their applicability to mutagenicity experiments that produce binomial responses from a control group and a single treated group. Attention is focused on experiments with (1) group sample sizes greater than 500 and (2) a probability less than .05 for a binary observation from any experimental unit being "positive." In addition, it is assumed that historical control data will not be included in the statistical analysis. The first analysis is a conditional binomial test, which has been tabulated extensively by Kastenbaum and Bowman [1970], while the second is based on a standard normal approximation to the distribution of the difference between two sample proportions. A formula is presented for each analysis that relates the associated probability of detecting a mutagen to the mutant frequencies and sample sizes of the two groups. Based on extensive numerical results, the conclusion is drawn that the normal test is the preferred analysis for experiments in which the ratio of the two sample sizes is between 0.80 and 1.25. On the further assumption that an experiment is to be conducted with equal experimental group sample sizes, recommendations are offered for values of this common sample size needed to achieve a specified power, ie, a degree of assurance of detecting a postulated level of mutagenic effect.

Animals↗
PubMed1994

Modulation of high-threshold transmission between heart interneurons of the medicinal leech by FMRF-NH2.

1. We examined high-threshold synaptic transmission between oscillatory pairs of leech heart interneurons. Inhibitory postsynaptic currents (IPSCs) could be reliably evoked by depolarizing the presynaptic neuron in voltage clamp from a holding potential of -35 mV. At this presynaptic potential, the Ca2+ currents underlying graded transmission are completely inactivated, and we conclude that a high-threshold Ca2+ current is extant in heart interneurons. Further evidence for this was that inhibitory postsynaptic currents were blocked when Co2+ replaced Ca2+ in the saline and thus high-threshold transmission was dependent on the presence of external Ca2+. 2. When IPSCs were evoked by a 200-ms duration voltage step from a holding potential of -35 mV in the presynaptic neuron, the time course of turn-on of the IPSC consisted of a fast (time-to-peak = 17.5 +/- 1.93 (SE) ms [n = 7]) and a slow (time-to-peak = 250 +/- 28.5 ms [n = 8]) component. FMRF-NH2 reduced the amplitude of the fast component but did not affect the slow component. When the presynaptic voltage step was ended the IPSC turned off with a single exponential time course. FMRF-NH2 slowed the time course of turn-off of the IPSC. 3. When IPSCs were evoked by a 1500-ms duration voltage step from a holding potential of -35 mV in the presynaptic neuron, these IPSCs peaked around 300 ms. Following the peak, the IPSC decayed with a single exponential time course. FMRF-NH2 accelerated the time course of this decay. At potentials of 0 mV and +5 mV, FMRF-NH2 produced a significant decrease in the peak current and at potentials of -5 mV and 0 mV, produced a significant decrease in the current integral. 4. High-threshold IPSCs could also be evoked by a spike in the presynaptic neuron. Bath application of 1 microM FMRF-NH2 decreased the amplitude of the spike-evoked IPSC and slowed the time course of its falling phase. 5. We examined the effect of FMRF-NH2 on the quantal synaptic transmission. Bath-application of FMRF-NH2 increased binomial p, the probability of release, and decreased binomial n, the number of units available for release. FMRF-NH2 had no effect on q, the unit size, when calculated from the distributions of PSPs, and increased the coefficient of variation (CV). 6. The lack of a change in q and the increase in CV suggested that FMRF-NH2 acted at a presynaptic location.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1999

Properties of threshold model predictions.

Estimation of genetic parameters and accuracy of threshold model genetic predictions were investigated. Data were simulated for different population structures by using Monte Carlo techniques. Variance components were estimated by using threshold models and linear sire models applied to untransformed data, logarithmically transformed data, and transformation to Snell scores. Effects of number of categories (2, 5, and 10), incidence of categories (extreme, moderate, and normal), heritability in the underlying scale (.04, .20, and .50), and data structure (unbalanced and balanced) on accuracy of genetic prediction were investigated. The real importance of using a threshold model was to estimate genetic parameters. An expected heritability of .20 was estimated to be .22 and .10 by a threshold model and a linear model, respectively. Accuracy increased significantly with a larger number of categories, a more normal distribution of incidences, increased heritability, and more balanced data. Even threshold models were shown to be more efficient with more than two categories (e.g., binomial). Transformation of scale did not accomplish the purpose intended.

Animal Husbandry↗
PubMed2002

A statistically valid alternative to the TDT.

OBJECTIVE: To present an alternative linkage test to the transmission/disequilibrium test (TDT) which is conservative under the null hypothesis and generally more powerful under alternatives. METHODS: The exact distribution of the TDT is examined under both the null hypothesis and relevant alternatives. The TDT is rewritten in an alternate form based on the contributions from each of the three relevant parental mating types. This makes it possible to show that a particular term in the estimate is an exact tie and thus to rewrite the estimate without this term and to replace the multinomial 'variance estimate' of Spielman et al. [Am J Hum Genet 1993;52:506-516] by the binomial variance. RESULTS: The resulting test is shown to be a stratified McNemar test (SMN). The significance level attained by the SMN is shown to be conservative when compared to the asymptotic chi(2) distribution, while the TDT often exceeds the nominal level alpha. Under alternatives, the proposed test is shown to be typically more powerful than the TDT. CONCLUSION: The properties of the TDT as a statistical test have never been fully investigated. The proposed test replaces the heuristically motivated TDT by a formally derived test, which is also computationally simple.

Data Interpretation, Statistical↗
PubMed2006

Determination of the carrier frequency of the common GJB2 (connexin-26) 35delG mutation in the Greek Cypriot population.

OBJECTIVE: Mutations in the GJB2 (connexin-26) gene are responsible for more than half of all cases of prelingual recessive inherited non-syndromic deafness in Europe. One specific mutation 35delG, accounts for up to 70% of the mutations detected in European populations and is one of the most frequent disease mutations identified so far. The aim of this study is to determine the percentage of carriers of this mutation in the Greek Cypriot population. METHODS: Genomic DNA was isolated from a total of 405 healthy unrelated Greek Cypriot adults. Screening for the frameshift 35delG mutation was performed by using an allele-specific PCR protocol. Moreover, using the Poisson probability distribution, we compared the carrier frequencies of the 35delG mutation of the Greek Cypriot population to the various European and Middle Eastern populations. RESULTS: The carrier frequency in the Greek Cypriot population was estimated to be 2.5% and is similar to that observed in other European populations. The variance estimate for 35delG mutation produces slightly wider intervals with the Poisson model when compared with Binomial probability variance estimate.

Adult↗
PubMed2001

The use of multilevel models to evaluate sources of variation in reproductive performance in dairy cattle in Reunion Island.

Sources of variation in measures of reproductive performance in dairy cattle were evaluated using data collected from 3207 lactations in 1570 cows in 50 herds from five geographic regions of Reunion Island (located off the east coast of Madagascar). Three continuously distributed reproductive parameters (intervals from calving-to-conception, calving-to-first-service and first-service-to-conception) were considered, along with one Binomial outcome (first-service-conception risk). Multilevel models which take into account the hierarchical nature of the data were used to fit all models. For the overall measure of calving-to-conception interval, 86% of the variation resided at the lactation level with only 7, 6 and 2% at the cow, herd and regional levels, respectively. The proportion of variance at the herd and cow levels were slightly higher for the calving-to-first-service interval (12 and 9%, respectively) - but for the other two parameters (first-service-conception risk and first-service-to-conception interval), >90% of the variation resided at the lactation level. For the three continuous dependent variables, comparison of results between models based on log-transformed data and Box-Cox-transformed data suggested that minor departures from the assumption of normality did not have a substantial effect on the variance estimates. For the Binomial dependent variable, five different estimation procedures (penalised quasi-likelihood, Markov-Chain Monte Carlo, parametric and non-parametric bootstrap estimates and maximum-likelihood) yielded substantially different results for the estimate of the cow-level variance.

Animals↗
PubMed1997

On the EM algorithm for overdispersed count data.

In this paper, we consider the use of the EM algorithm for the fitting of distributions by maximum likelihood to overdispersed count data. In the course of this, we also provide a review of various approaches that have been proposed for the analysis of such data. As the Poisson and binomial regression models, which are often adopted in the first instance for these analyses, are particular examples of a generalized linear model (GLM), the focus of the account is on the modifications and extensions to GLMs for the handling of overdispersed count data.

Algorithms↗
PubMed2004

Seroepidemiology of neosporosis in dairy cattle in Uruguay.

A seroepidemiological survey of Neospora caninum was done in a dairy farm in Uruguay employing indirect fluorescent antibody test (IFAT). Sera from 217 cattle (155 cows, 31 heifers and 31 calves) were tested for N. caninum antibodies in July 2000 and it was found that abortions were significantly associated with the seropositivity of the cows by chi(2)-test (P = 0.025). The cows with an IFAT titre of 1:3200 were at a significantly higher risk of abortion than seronegative cows (P = 0.0013). Neospora organisms were detected in the brains of two aborted foetuses by immunohistochemical examination. The infection of N. caninum was considered postnatal because of the even distribution of seropositive cows (60%), low seroprevalence (20%) in calves and no significant correlation in the serostatus between calves and their dams (P = 0.43). A fitted binomial generalised linear model revealed that there was an increasing risk of abortion with increasing IFAT titre and increasing age between 2 and 6 years.

Abortion, Veterinary↗
PubMedDate not supplied

[Risk behaviours and seroprevalence to HIV, HBV and HCV in patients of the AIDS information and prevention center in Valencia, Spain].

OBJECTIVE: The purpose of this study was to describe the sociodemographic and serologic profiles in a first time consultant population at the Information and AIDS Prevention Center of Valencia (Spain). In addition, the HIV infection risk factors were analyzed. METHOD: A cross-sectional study was performed on 1,573 persons who consulted during the year 1995. Sociodemographic and infection risk practices data were recorded and serologic information about HIV, HBV and HCV infection were obtained. Exact binomial method with a 95% interval confidence was used to calculate infection prevalence and the chi square test to make comparisons between qualitative variables. RESULTS: Sex distribution was 66,1% males and 31,9% females; mean age was 29,01 (SD: 9.2) years. Sexual intercourse without condom (25.2%) and parenteral drug abusers (22.6%) were the more frequent risk groups seeking consultation about HIV infection. Global HIV infection prevalence was 12.7% (95% CI= 11,2-14,5%). Among HIV seropositive patients, sexual transmission accounted for 30.8% of cases, of which 69.4% were heterosexual relations. The HIV infection prevalence for different risk groups were the following: parenteral drug abusers 36.8% (95% CI= 31,7-42%), heterosexual intercourse with an HIV-infected partner 24.1% (95% CI= 17,1-32,2%) and homosexual intercourse between men 9,5% (95% CI= 5,8-14,5%). HCV antibody prevalence for parenteral drug abusers was 81.2% (95% CI= 76,7-85,1%). Risk practices with a statistically significant association with HIV infection were: being an injecting drug abuser, as well as having an HIV infected and/or a injecting drug abuser partner. CONCLUSIONS: Drug parenteral abusers are still the target population for prevention programs. Data suggest that prevention and sexual education programs must continue. The main effort should be focused on the young population and on sexual partners of injecting drug abusers and/or HIV seropositive partners.

Adolescent↗
PubMed1975

Estimates of statistical release parameters from crayfish and frog neuromuscular junctions.

1. Transmitter release at crayfish and frog neuromuscular junctions was studied by recording synaptic potentials with extracellular or intracellular glass micro-electrodes. 2. The binomial release parameters n and p were calculated using the experimental observations for the mean number of quanta (m) released in a series of trials, the variance (var) of the quantum content distribution and the number of transmission failures (n-o). 3. In one series of experiments on frog neuromuscular junction, action potentials were blocked by tetrodotoxin. Transmitter release was limited to a circumscribed part of the nerve terminal by focal stimulation with a glass micro-electrode. Values for m were between 0-6 and 5-7 and calculated values for n ranged from 3 to 23. p was between 0-05 and 0-48. In a second series of experiments on frog neuromuscular junction transmitter release was evoked by conventional stimulation of the nerve trunk in Mg-Ringer. m was mostly between 20 and 60 and in the same experiments n was calculated to be between 70 and 125. Values for p ranged from 0-25 to 0-48. 4. It can be concluded from the present results that transmitter release at frog neuromuscular junction is described by binomial statistics as is the case for neuromuscular junction of crayfish. 5. In comparing the values for n for the two series of experiments on frog neuromuscular junction it appears that n is dependent on the length of the activated synaptic contact. The numbers for n calculated from frog neuromuscular junction are of the same order of magnitude as the number of 'active zones' seen in the corresponding length of the synaptic nerve terminal.

Action Potentials↗
PubMed2004

Obtaining single cells: analysis and evaluation of an experimental protocol by means of a simulation model.

The research presented in this paper analyses a newly developed experimental protocol for isolating single cells by constructing a simulation model of the process. The protocol involves sequential 50% dilutions of a cell suspension in a microtiter plate, so that eventually, wells are obtained containing exactly one cell. The aim of this modelling study is (i) to gain insight in the governing mechanisms of the dilution process, (ii) to confirm experimental findings and (iii) to enable the prediction of an average outcome for future experiments. The model construction process is presented chronologically. The initial basic model simulates the experiment as a sequence of binomial processes, using Monte Carlo techniques. Statistical analysis of the results shows that aggregational factors need to be taken into account in the form of a lognormal distribution. Several issues involved in this adaptation are discussed. To fully account for cell aggregation in the dilution process, a cell clumping algorithm is built into the simulation model. Simulation data from the resulting model show similar statistical characteristics as the experimental data and yield reliable prediction intervals for the available experimental data. The simulation model is a useful tool to support experimental findings and predict the outcome of future experiments. Even more importantly, this study emphasises the importance of careful statistical analysis in single cell research. The impact of stochastic effects is considerably amplified at the low cell concentrations involved and needs to be taken into account in any modelling effort.

Bacteria↗
PubMed2006

Use of the psychological inventory of criminal thinking styles to predict disciplinary adjustment in male inmate program participants.

The Psychological Inventory of Criminal Thinking Styles (PICTS) was administered to program participants in two different federal prisons-a medium-security federal correctional institution and a maximum-security penitentiary-who were subsequently followed for a period of 24 months for evidence of disciplinary adjustment problems. Disciplinary outcome was measured by the total number of incident reports, the number of nonaggressive incident reports, and the number of aggressive incident reports received during the 24-month follow-up. Negative binomial regression was used to test the relationship between the eight PICTS thinking style scales and three disciplinary outcome measures because the total and nonaggressive disciplinary report distributions showed signs of overdispersion. The only PICTS thinking style scale to achieve statistical significance in this study was the Cutoff scale that successfully predicted total, nonaggressive, and aggressive incident reports in both samples.

Adult↗
PubMed1993

A gamma model for extra-binomial variation in dilution assays.

Dilution assays are widely used to estimate the concentration of a particular type of cell, called a limiting cell, in a population of cells from an animal. For each animal, the response vector is a set of binomial variables derived at different plating frequencies. Often extra-binomial variation is found when dilution assay data are analysed. This paper proposes a mixture model where the animal level effects are assumed to have a gamma distribution. This leads to more realistic standard errors for the estimates of the limiting cell concentrations.

Animals↗
PubMed2003

Design of Phase II cancer trials evaluating survival probabilities.

BACKGROUND: Phase II cancer studies are undertaken to assess the activity of a new drug or a new treatment regimen. Activity is sometimes defined in terms of a survival probability, a binary outcome such as one-year survival that is derived from a time-to-event variable. Phase II studies are usually designed with an interim analysis so they can be stopped if early results are disappointing. Most designs that allow for an interim look are not appropriate for monitoring survival probabilities since many patients will not have enough follow-up by the time of the interim analysis, thus necessitating an inconvenient suspension of accrual while patients are being followed. METHODS: Two-stage phase II clinical trial designs are developed for evaluating survival probabilities. These designs are compared to fixed sample designs and to existing designs developed to monitor binomial probabilities to illustrate the expected reduction in sample size or study length possible with the use of the proposed designs. RESULTS: Savings can be realized in both the duration of accrual and the total study length, with the expected savings increasing as the accrual rate decreases. Misspecifying the underlying survival distribution and the accrual rate during the planning phase can adversely influence the operating characteristics of the designs. CONCLUSION: Two-stage phase II trials for assessing survival probabilities can be designed that do not require prolonged suspension of patient accrual. These designs are more efficient than single stage designs and more practical than existing two-stage designs developed for binomial outcomes, particularly in trials with slow accrual.

Clinical Trials, Phase II as Topic↗
PubMed2006

Approaches for sampling the twospotted spider mite (Acari: Tetranychidae) on clementines in Spain.

Tetranychus urticae Koch (Acari: Tetranychidae) is an important pest of clementine mandarins, Citrus reticulata Blanco, in Spain. As a first step toward the development of an integrated crop management program for clementines, dispersion patterns of T. urticae females were determined for different types of leaves and fruit. The study was carried out between 2001 and 2003 in different commercial clementine orchards in the provinces of Castelló and Tarragona (northeastern Spain). We found that symptomatic leaves (those exhibiting typical chlorotic spots) harbored 57.1% of the total mite counts. Furthermore, these leaves were representative of mite dynamics on other leaf types. Therefore, symptomatic leaves were selected as a sampling unit. Dispersion patterns generated by Taylor's power law demonstrated the occurrence of aggregated patterns of spatial distribution (b > 1.21) on both leaves and fruit. Based on these results, the incidence (proportion of infested samples) and mean density relationship were developed. We found that optimal binomial sample sizes for estimating low populations of T. urticae on leaves (up to 0.2 female per leaf) were very large. Therefore, enumerative sampling would be more reliable within this range of T. urticae densities. However, binomial sampling was the only valid method for estimating mite density on fruit.

Animals↗
PubMed2006

An ecological study of tuberculosis transmission in California.

OBJECTIVES: We evaluated the association between ecological factors and rates of tuberculosis within California, using pediatric tuberculosis as an indicator of new transmission. METHODS: Ecological variables such as racial/ethnic distribution, immigration level, education, employment, poverty, and crowding were obtained from the United States Census for each census tract in California. These data were incorporated into a negative binomial regression model with the rate of pediatric tuberculosis disease in each census tract as an outcome variable. Disease rates were obtained by geocoding reported cases. Subsections of the state (San Francisco and Los Angeles) were examined independently. RESULTS: Census tracts with lower median incomes, more racial/ethnic minorities, and more immigrants had higher rates of pediatric tuberculosis. Other frequently cited risk factors such as overcrowding and unemployment were not associated with increased disease after adjusting for other measures. Risks were comparable across regions, but subtle differences were noted. CONCLUSIONS: The techniques used in this work provide a way to examine a disease within its social context. The results confirmed that tuberculosis in California continues to be a disease of poverty and racial/ethnic minorities.

Adolescent↗
PubMed1982

[Model of mediator secretion at a neuromuscular synapse based on the spatial heterogeneity of the probability of acetylcholine quantum release].

A spatial heterogeneity of the probability of the mediator quantum release (pt) along the nerve terminal was found in experiments on frog sartorius muscle with extracellular recording of end-plate potentials. The expression of Ca2+ ions effect depended upon the initial pt. With intracellular recording the increase of Ca2+ concentration from 0.2 to 1.8 mM was accompanied by increase of n and p binomial parameters. On the basis of the obtained data a model of mediator release at neuromuscular synapsis is proposed, which allows the estimation of the coefficients of pt distribution along the nerve terminal and the number of acting release sites. For estimation of these parameters it is necessary to calculate the n and p at two different Ca2+ ion concentrations.

Acetylcholine↗