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 307 records · Page 17Linked to original sources
PubMed2003

Multiple n = 1 trials in the identification of responders and non-responders to the cognitive effects of Ginkgo biloba.

OBJECTIVE: A pilot study to assess multiple crossover n = 1 trials with verum/placebo discrimination as the outcome measure as a means of identifying responders and non-responders to the acute nootropic effect of Ginkgo biloba (G. biloba) among healthy volunteers. METHOD: Multiple double-blind, placebo-controlled n = 1 trials with 8 treatments in randomized order and separated by minimum washout periods of 7 days. Treatments were acute 120 mg doses of G. biloba extract (GK501) or undistinguishable placebo. The frequency distribution of correct scores for verum-placebo discrimination was compared with the binomial distribution to identify putative responders, who were then tested for consistency of performance over a further 8 treatments. RESULTS: The frequency distribution of scores (n = 11) was bimodal and a discontinuity defined 3 putative responders and 2 putative negative responders for re-test. Two of the putative responders again performed at above chance level and the probability of achieving their scores or better by chance was 0.013 and 0.052. CONCLUSIONS: n = 1 trials with verum/placebo discrimination as outcome are a promising method for exploring response heterogeneity to treatments with a subjective effect. Preliminary evidence suggests that there are responders and non-responders to an acute G. biloba treatment among healthy subjects.

Adult↗
PubMed1980

A stochastic model for the occurrence of transient ischemic attacks.

This paper presents the development, application and evaluation of a stochastic model of the frequency of occurrence of transient ischemic attacks (TIAs). TIAs occur during periods of abnormal arterial activity. The TIAs which occur during a single period of abnormal activity are called a cluster of TIAs. Thus, the number of TIAs occurring in a time interval is determined by the number of clusters of TIAs occurring and the number of TIAs per cluster. The distribution of the number of clusters, which is a modification of the Poisson distribution, is obtained through the use of infinitesimal probabilities and the method of generating function. The number of TIAs per cluster follows the logarithmic series distribution. The distribution of the number of TIAs is then a modification of the negative binomial distribution, which allows for censoring of the data that may be related to the occurrence of the clusters of TIAs. Estimates for the parameters, based on observed frequencies, are obtained, which allow the model to be applied to data from the Aspirin in Transient Ischemic Attacks Study.

Aspirin↗
PubMed1992

Analysis of fluctuations of "minimal" excitatory postsynaptic potentials during long-term potentiation in guinea pig hippocampal slices.

In previous studies, quantal analysis assuming a simple binomial model has shown that long-term potentiation (LTP) is accompanied by an increase in both mean quantal content (m) and quantal size (v), whereby the increase in m predominates. In the present study, "compound" binomial distributions with variable probabilities were convolved with Gaussian distributions in computer experiments to simulate amplitude histograms of intracellular excitatory postsynaptic potentials (EPSPs). A deconvolution procedure assuming equal "quantal" separation (v) between discrete components, but without assuming binomial statistics, was applied to the simulated distributions to determine v. It was found that with a small ratio of standard deviation of noise to v (Sn/v less than 0.4), a reliable estimate of v can be obtained even for small samples (N = 100). When Sn/v was larger (0.4-0.6), approximate v estimates (within +/- 10-20% of the simulated v) could be obtained by averaging estimates from about 10 small samples (N = 100). "Minimal" EPSPs were recorded in area CA1 of guinea pig hippocampal slices. 37 EPSP amplitude samples of 9 neurones were measured before and up to 55 min after 10 tetanizations of stratum radiatum. In accordance with the previous data, the increase in v accounted for only about 10% of the average post-tetanic increase in EPSP amplitude and was not correlated with the latter. However, for an EPSP subset with small LTP magnitude, the increase in v accounted for an essential part of the LTP magnitude while the increase in m did not correlate with it. The results are in agreement with previous data obtained in the context of the simple binomial model and are interpreted as indicating primarily a presynaptic mechanism of LTP maintenance. The results suggest two types of synaptic mechanism of LTP maintenance related to the increases in m and v, respectively. The latter mechanism is saturated at about 10 to 30% increase in post-tetanic amplitude above the pre-tetanic EPSP amplitude.

Animals↗
PubMed1991

Pooling controls from different studies.

This paper develops a method for estimating the odds ratio in a case-control study that 'borrows' strength from the controls in similar previous studies. We assume that the observations within each stratum in the current study are generated from a pair of independent binomial distributions. We assume that the observations on the controls, again within each stratum and from the previous studies, are independent binomial random variables. We use these controls to construct a prior distribution for the stratum specific log-odds for the controls in the current study which we then combine with the likelihood from the current study to arrive at the posterior distribution of the target quantities of interest, the adjusted or stratum specific log-odds ratios. We assume a diffuse prior distribution for the stratum specific log-odds ratio. A simulation study investigates the frequency or repeated sampling properties of the inference based upon the posterior distribution of the log-odds ratio so constructed.

Bayes Theorem↗
PubMed1975

Population biology of Camallanus oxycephalus Ward and Magath, 1916 (Nematoda: Camallanidae) in white bass in western Lake Erie.

The distribution and abundance of the nematode Camallanus oxycephalus infecting white bass, Morone chrysops, in western Lake Erie was studied for over 2 years. Infection was generally more frequent and of higher intensity in large fish. The frequency distributions of nematode abundance in all segments of the fish population followed the negative binomial distribution. The data show seasonal cycles in population structure, site selection, intensity of infection, maturation, and reproduction. Infection occurs during July and August with a resulting peak in population density; during late summer and autumn, mortality, probably density-dependent, reduces the population by 30 to 60%; surviving worms are eliminated at 1 year of age. Growth and development of female worms is arrested from November to April, then proceeds at a rapid rate until the worms release their larvae and die. This growth pattern is probably related to temperature but may also involve host hormone cycles. The dispersal period of the nematode coincides with the annual maximum density of the intermediate host, a cyclopoid copepod,and is interpreted as an adaptation which increases the probability of successful transmission. Because the number of larvae produced by each female worm is a function of body volume, natural selection has favored rapid spring growth and attainment of large body size relative to the male worm. Both seasonal timing in the life cycle and the number of larvae produced are important factors in determining the abundance of this and perhaps other parasites. Evidence is presented suggesting that fluctuations of environmental parameters may disrupt the timing of transmission and alter the distribution and abundance of the parasite. It is hypothesized that the magnitude of such changes in parasite abundance may be related to the complexity of the host-parasite system.

Animals↗
PubMedDate not supplied

[Patterns of host-parasite interactions between the nematode Heligmosomum mixtum (Schulz, 1952) and the bank vole (Clethrionomys glareolus Schreber, 1780)].

Some aspects of the host-parasite interaction of the nematode Heligmosomum mixtum and the bank vole have been studied. The dependence of infestation on the host sex, age and weight, the seasonal and annual abundance dynamics are investigated. It has been found that the bank vole is the main host of H. mixtum; the distribution of H. mixtum abundances in the host population is described by a negative binomial distribution model. The greatest infestation is characteristic for mature bank voles; males are infected more heavily than females. Infestation with the nematode increases alongside with the host weight. Seasonal dynamics of the nematode abundance in a bank vole population appears as a curve with a maximum in January and a minimum in August; the infestation curve for 1-month-old animals captured from June through October has two peaks (in July and October), with a minimum in June. The number of parasites in the ecosystem over a long-term period changed synchronously with the host abundance. The synchronism in the host-parasite system dynamics is possible when the parasite has a short life span, and does not influence the host abundance.

Animals↗
PubMedDate not supplied

[Laboratory animal infection in modeling intestinal schistosomiasis].

A comparative efficiency of different regimes for infecting laboratory animals has been determined in order to find out optimal conditions under which an experimental model of intestinal schistosomiasis (infection with Schistosoma mansoni) can be maintained. When evaluating the results of laboratory definitive hosts infection we took into account the character of Schistosoma distribution in animals, which with high probability rate was modelled by means of negative binomial distribution. The main parameters of this distribution were used for determination of effective doses and methods of animals infection alongside with generally accepted indices of infection rate and intensiveness. Analysis of the data obtained has shown that the infection of 150 cercarians per mouse and 200 cercarians per golden and striped hairy-footed hamster by their subcutaneous administration creates optimal density of parasites in the host. Results of investigations have shown that striped hairy-footed hamsters can be used as definitive hosts of Schistosoma.

Animals↗
PubMed2000

The inference of antigen selection on Ig genes.

Analysis of somatic mutations in V regions of Ig genes is important for understanding various biological processes. It is customary to estimate Ag selection on Ig genes by assessment of replacement (R) as opposed to silent (S) mutations in the complementary-determining regions and S as opposed to R mutations in the framework regions. In the past such an evaluation was performed using a binomial distribution model equation, which is inappropriate for Ig genes in which mutations have four different distribution possibilities (R and S mutations in the complementary-determining region and/or framework regions of the gene). In the present work, we propose a multinomial distribution model for assessment of Ag selection. Side-by-side application of multinomial and binomial models on 86 previously established Ig sequences disclosed 8 discrepancies, leading to opposite statistical conclusions about Ag selection. We suggest the use of the multinomial model for all future analysis of Ag selection.

Antigens↗
PubMed1985

Adhesive interactions between normal and dystrophic human skin fibroblasts.

The adhesive properties of skin fibroblasts from patients with Duchenne muscular dystrophy (DMD) were studied by analysing cell aggregate formation in suspensions consisting of normal and DMD fibroblasts. By the use of aggregation kinetics and fluorescent labelling, the genotypic composition of aggregates in mixed-cell suspensions could be visualised. The distribution of normal and DMD cells within these aggregates could then be compared to theoretical binomial distributions which assume no difference in the specific adhesiveness between the two genotypes. Analysis of the 3- and 4-cell aggregates which were produced by co-aggregating normal and DMD cells demonstrate that there is no qualitative (specific) difference in the adhesiveness between normal and DMD fibroblasts. However, quantitative changes in the cell-cell adhesion of DMD fibroblasts may be present, and this is supported by the relatively small proportion of intermediate size heterotypic aggregates which were formed in mixed-genotype cell suspensions. In such mixtures, fewer aggregates consisting of 5 or more cells were formed compared to fibroblast suspensions derived from pairs of normal individuals. Furthermore, cell suspensions from pairs of DMD patients produced even less greater than or equal to 5-cell aggregates than were found in the mixed-genotype experiments. These findings are considered in relation to previous reports of abnormal cell adhesiveness and other adhesion-related mechanisms in DMD cells.

Animals↗
PubMed2001

Number-between g-type statistical quality control charts for monitoring adverse events.

Alternate Shewhart-type statistical control charts, called "g" and "h" charts, are developed and evaluated for monitoring the number of cases between hospital-acquired infections and other adverse events, such as heart surgery complications, catheter-related infections, surgical site infections, contaminated needle sticks, and other iatrically induced outcomes. These new charts, based on inverse sampling from geometric and negative binomial distributions, are simple to use and can exhibit significantly greater detection power over conventional binomial-based approaches, particularly for infrequent events and low "defect" rates. A companion article illustrates several interesting properties of these charts and design modifications that significantly can improve their statistical properties, operating characteristics, and sensitivity.

Cross Infection↗
PubMed2002

Determinants of handedness in twins.

It is well established that the distribution of the combinations of handedness (LL, LR, and RR) in twin pairs is roughly binomial regardless of zygosity or sex. This fact has challenged current genetic models of handedness. We show here that: (a) there must be at least one environmental determinant of handedness; and (b) the binomial distribution does not in itself invalidate genetic models of handedness. In singletons, left-handedness is strongly associated with low birth weight. In twins, this association is weaker (apparently as a consequence of a stronger association with birth order--i.e., with being first-born--within the pair). We speculate that the hazards associated with being first-born in twin pairs (e.g., trauma) are more closely associated with left-handedness than are the hazards associated with being second-born (e.g., hypoxia).

Journal Article↗
PubMed2005

The role of competition and clustering in population dynamics.

A simple argument based on the distribution of individuals amongst discrete resource sites is used to show how the form of single species population models depends on the type of competition between, and the spatial clustering of, the individuals. For scramble competition between individuals, we confirm earlier demonstrations that the Ricker model is a direct consequence of a uniform random distribution of individuals across resources. By introducing spatial clustering of individuals according to a negative binomial distribution, we are able to derive the Hassell model. Furthermore, the tent map model is seen to be a consequence of scramble competition and an ideal-free distribution of individuals. To model contest competition under different degrees of spatial clustering we derive a new three-parameter model, of which the Beverton-Holt and Skellam models are special cases, where one of the parameters relates directly to the clustering distribution. Other population models, such as the quadratic model and the theta-Ricker models, cannot be derived in our framework. Taken together our derivations of population models allows us to make a more rigorous prescription for model choice when fitting to particular datasets.

Animals↗
PubMed1991

Influence of host strain and helminth isolate on the first phase of the relationship between rats and Moniliformis moniliformis (Acanthocephala).

Eleven trials, involving 440 rats bred from 3 laboratory strains and worms from 4 isolates of Moniliformis moniliformis, were carried out with each rat receiving an oral dose of 15 cystacanths. The results showed that the infectivity of the cystacanths was not affected by their age (range 55-194 days) or by their density per cockroach during development (16.1-88.6 cystacanths per cockroach). The numbers of worms per rat recovered at 35 days postinfection (p.i.) were shown to be related to rat strain, with highly inbred strains (PVG and F344) being more supportive of numbers of worms than an outbred Wistar strain. There was no evidence to suggest that the sex of the rats had any influence on the numbers of worms recovered at 35 days p.i. Evidence was obtained to suggest that smaller (younger) rats are likely to support more worms on average than larger (older) rats. There was no evidence of any relationship between worm weight and numbers of worms present per rat on day 35 p.i. Generally, rat strain had little effect on the dry weight (growth) of male M. moniliformis, in contrast to observations made for female worms. The greatest range of worm weights was observed from the recent isolate of the worm (1982) as compared with the well established isolate (1956) and the rats that supported most worms differed from those that harbored the largest worms. Rat sex was not observed to be associated with worm weight. The frequency distributions of numbers of M. moniliformis per rat were not described readily by the negative binomial distribution.

Analysis of Variance↗
PubMed2000

The bystander effect in photodynamic inactivation of cells.

Treatment of MDCK II cells with the lipophilic photosensitizer tetra(3-hydroxyphenyl)porphyrin and light was found to induce a rapid apoptotic response in a large fraction of the cells. Furthermore, the distribution of apoptotic cells in microcolonies of eight cells was found to be different from the binomial distribution, indicating that the cells are not inactivated independently, but that a bystander effect is involved in cell killing by photodynamic treatment. The observation of a bystander effect disagrees with the common view that cells are inactivated only by direct damage and indicates that communication between cells in a colony plays a role in photosensitized induction of apoptosis. The degree of bystander effect was higher for cells dying by necrosis than for cell dying by apoptosis.

Animals↗
PubMed1990

Epidemiology and immunology of Necator americanus infection in a community in Papua New Guinea: humoral responses to excretory-secretory and cuticular collagen antigens.

Baseline data from an immuno-epidemiological study of hookworm infection in a rural village in Madang Province, Papua New Guinea are reported. Necator americanus was found to be the commonest helminth infection, with a prevalence of near 100% and intensity of 40 worms per host in adults. Enterobius vermicularis, Ascaris lumbricoides and Trichuris trichiura were also present, at prevalences of 53, 10 and 3% respectively; Ancylostoma duodenale was absent. The frequency distribution of N. americanus was highly over-dispersed, and was well described by a negative binomial distribution with aggregation parameter, k, of 0.370. Intensity of infection was significantly related to host age, but did not differ between the sexes. Haemoglobin levels and haematocrit values were indicative of anaemia in the community, but were unrelated to hookworm infection. Levels of antibodies (IgG, IgA and IgM combined) against adult Necator cuticular collagen and excretory-secretory (ES) products were determined. Serum concentrations of the two types of antibody were significantly correlated with each other. Significant positive correlations were found between anti-ES antibody levels and hookworm egg production, and between anti-collagen antibody levels and host age. It is suggested that the level of anti-collagen antibodies may reflect cumulative exposure to infection, whereas levels of anti-ES antibodies may be more dependent on current worm burden. No evidence was found to suggest that either antibody response is important in regulating parasite population growth. Similarly, the presence of a positive correlation between eosinophil concentration and infection intensity in adults indicates that eosinophilia reflects, rather than determines, the host's worm burden.

Adolescent↗
PubMed1978

Factors affecting serum IgA antibody to Epstein-Barr viral capsid antigens in nasopharyngeal carcinoma.

Irrespective of the ethnic origin of the patient, nasopharyngeal carcinoma (NPC), appears to stimulate the production of IgA antibodies against VCA. These antibodies are detected at high frequency and titres in sera from NPC patients but only rarely from control subjects. A majority of relapse-free survivors tested 1-12 years after radiotherapy (RT) sustain a detectable level of IgA anti-VCA. Serum titres of IgA anti-VCA remain relatively unchaged in individual NPC patients after RT, regardless of the disease evolution. These antibodies were detected in serum from one individual 9 months before NPC and the titre rose concomitantly with its clinical onset. Titres of IgA anti-VCA in multiple serum specimens from individual NPC patients, and in sera from different NPC patients, do not correlate with titres of IgG anti-VCA or with Serum IgA. It thus seems possible that the IgA anti-VCA in the sera of NPC patients might be largely derived near NPC. Apparently healthy individuals showing detectable IgA anti-VCA tend to aggregate in families of NPC patients. The distribution of siblings of these families who have the IgA anti-VCA reaction shows the binomial distribution expected for an autosomal recessive trait, implying the involvement of an autosomal recessive gene in the IgA anti-VCA response.

Antigens, Viral↗
PubMed2001

Fractional Fokker-Planck equation and oscillatory behavior of cumulant moments.

The Fokker-Planck equation is considered, which is connected to the birth and death process with immigration by the Poisson transform. The fractional derivative in time variable is introduced into the Fokker-Planck equation in order to investigate an origin of oscillatory behavior of cumulant moments. From its solution (the probability density function), the generating function (GF) for the corresponding probability distribution is derived. We consider the case when the GF reduces to that of the negative binomial distribution (NBD), if the fractional derivative is replaced to the ordinary one. The H(j) moment derived from the GF of the NBD decreases monotonically as the rank j increases. However, the H(j) moment derived in our approach oscillates, which is contrasted with the case of the NBD. Calculated H(j) moments are compared with those of charged multiplicities observed in pp, e(+)e(-), and e(+)p collisions. A phenomenological meaning of introducing the fractional derivative in time variable is discussed.

Journal Article↗
PubMed1978

Statistical aspects of the treponemal counts in the TPI test.

A method of counting treponemes in randomly selected visual fields is described. It was found that Treponema pallidum is distributed as a Poisson distribution among the visual fields and also among samples drawn from the same suspension. Immobilized treponemes are binomally distributed among the total number of treponemes. Application of the parameters of the Poisson and the binomial distributions should be made in order to determine the dosage of T. pallidum in animal experimentation and to evaluate the outcome of the TPI test. Some statistical aspects of the investigation of treponemal survival are presented.

Probability↗