Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “confidence limits”

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 55 records · Page 3Linked to original sources
PubMed1992

Confidence limits for the parameter estimation in the dipole localization method on the basis of spatial correlation of background EEG.

A new residual function in the inverse problem of equivalent dipole localization methods is proposed which is based on the spatial correlation of the background EEG. This residual has the advantage that it allows the calculation of confidence limits for dipole model parameters. The method was applied to VEP data, and it was studied how the localization precision depends on the recording time of the EEG. It was found that the tangential position of an equivalent dipole can be located at 99% confidence in a region of the order 7 x 7mm for a head radius of 10cm, while the 99% confidence interval of the depth estimate is approximately 1cm, with a recording time of 20 minutes. It was also observed that an EEG recording time of more than 10-15 minutes is needed to obtain stable localization precision estimates.

Brain↗
PubMed1985

Noise exposure--sample size and confidence limit calculation.

In a previous paper a method for assessing noise exposure levels of workers from the same trade was presented. There was also discussed how to apply the NIOSH sample size method to noise exposed populations. In this paper both subjects are further discussed by including the calculation of confidence limits for the mean noise exposure as well as for the percentage of workers with noise exposure levels beyond a certain level. The calculation of the sample size of a population where standard deviation is known is also discussed.

Environmental Exposure↗
PubMed1984

APL programs for outcome probabilities and confidence limits in sequential binomial trials.

For closed sequential binomial sampling plans (including plans for multistage sampling), the probability of reaching each terminal point is calculated. These probabilities are cumulated from "each side" of the plan. Thus, the power function obtainable by defining any (reasonable) acceptance region can be studied. Corresponding to a given outcome of the trial confidence limits can be calculated by an auxiliary program.

Clinical Trials as Topic↗
PubMed1993

Upper confidence limits on excess risk for quantitative responses.

The definition and observation of clear-cut adverse health effects for continuous (quantitative) responses, such as altered body weights or organ weights, are difficult propositions. Thus, methods of risk assessment commonly used for binary (quantal) toxic responses such as cancer are not directly applicable. In this paper, two methods for calculating upper confidence limits on excess risk for quantitative toxic effects are proposed, based on a particular definition of an adverse quantitative response. The methods are illustrated with data from a dose-response study, and their performance is evaluated with a Monte Carlo simulation study.

Animals↗
PubMed2000

Proportion estimation with confidence limits.

A common task in microbiology involves determining the composition of a mixed population of individuals by drawing a sample from the population and using some procedure to identify the individuals in the sample. There may be a significant probability that the identification procedure misidentifies some members of the sample (for example, because the available data are insufficient unambiguously to identify an individual) which makes finding the proportions in the underlying population non-trivial. A further complication arises where individuals are present in the population that do not belong to any of the subpopulations recognised by use of the identification procedure. A simple algorithm is presented to address these problems and construct a maximum likelihood estimate of the proportions, together with confidence limits. The technique is illustrated using an example drawn from flow cytometry in which phytoplankton cells are identified from flow cytometry data by an RBF neural network, and the limitations of the approach are discussed.

Confidence Intervals↗
PubMed1985

Confidence limits for probability of response in multistage phase II clinical trials.

Herson (1979, Biometrics 35, 775-783) has given a method for designing one-arm k-stage phase II clinical trials, which permits early termination of the trial if the treatment is apparently ineffective, while retaining acceptable levels of power and significance. This paper gives a method for calculating the confidence limits on the response proportion, conditional on a particular study design.

Drug Evaluation↗
PubMed1992

Confidence limit analyses should replace power calculations in the interpretation of epidemiologic studies.

Frequently, after an epidemiologic study is completed, statistical power to detect a relative risk of interest is recalculated using data obtained during the course of the study. A negative study may then be dismissed on the grounds that its power was too low. However, post hoc power calculations ignore the actual relative estimate and its variance, which are by then known. We present evidence that post-study power calculations have little value and should be replaced by a more informative method using the upper (1 - alpha)% confidence limit of the point estimate that touches the value of the relative risk of interest.

Confidence Intervals↗
PubMed1982

Incidence of disorders tested by systematic screening: confidence limits and comparison of programmes.

Using the data from screening done in Switzerland since 1965, we showed that the probability of finding cases with increased phenylalanine or leucine concentrations is compatible with a Poisson distribution. If there are no trends present from year to year and if the Poisson distribution is an accurate fit further statistical treatment is possible. The advantage of using the Poisson distribution is exemplified by the calculation of confidence limits for the incidence of hyperphenylalaninaemia, maple syrup urine disease and hypothyroidism. Furthermore, statistical comparisons between different screening programs are easily done.

Epidemiologic Methods↗
PubMed1982

Quantification, smoothing, and confidence limits for single-units' histograms.

In this article the relationships among firing rate, probability of firing and counts per bin are examined. It is suggested that PSTHs, autocorrelations and crosscorrelations of neuronal activity should all be expressed in units of firing rates (spikes/s), since the values obtained by such scaling are independent of bin size and of total time of measurement. A simple method for these histograms is described. Methods to compute confidence limits for PSTHs, autocorrelations and crosscorrelations are suggested. The computations are based on the null hypothesis that the spike train(s) is (are) the realization of (independent) Poisson-point process(es). The validity and the limitations of these computations methods, when applied to spike trains, are discussed. Methods to smooth out random fluctuation with little distortion of the histogram's shape are described. It is suggested that one can minimize the distortion of the histogram in the time-domain and in the frequency-domain by using a bell-shaped bin whose center point slides continuously along the histogram. The article aims at giving the potential user of the methods some insight for the meaning of the formulae. It describes in detail how the methods are applied in practice and illustrates each method by using real data from single-unit recordings.

Animals↗
PubMedDate not supplied

Defining absolute confidence limits in the identification of Caulobacter proteins by peptide mass mapping.

A derivatization reaction, guanidination, was recently reported that increases MALDI-TOF MS sensitivity toward lysine-terminated peptides. Its application conveys sequence information that can be used as a parameter in peptide mass mapping database searches. This paper presents a systematic study of the impact of guanidination on proteomic analysis of an entire bacterial organelle. Sixty-two 2-D gel isolated proteins from Caulobacter crescentus stalks were studied. A novel computer algorithm, Prodigies, was developed to analyze the data. Absolute confidence limits associated with protein assignments were established using Monte Carlo simulations of database searches. The advantages of guanidination are illustrated using both experimental and theoretical data.

Algorithms↗
PubMed1993

Confidence limits on the branching order of phylogenetic trees.

We describe a confidence test for branching order that can aid protein phylogeny reconstruction as well as the evaluation of the optimal tree. It is proposed that the process resulting in the observed amino acid residue differences, which is the basis for the identification of the order and relative times of divergence events, is appropriately described by a modification of the negative binomial distribution. The relative total numbers of mutations (accepted and nonaccepted), which result in a given number of amino acid differences, may be obtained as the expectation of this distribution. The associated variances enable significant differences in tree branching order to be established. If the total rates of mutation of the genes encoding the compared proteins are equal, the expected total mutations and their associated variances map identically to their relative times of divergence. In addition, significantly different rates of change (due to differences in total mutation rate and/or acceptance rate) may be identified without the requirement of outlying reference group. The method is equally applicable to phylogenies derived from DNA or RNA sequence information.

Amino Acid Sequence↗
PubMed1977

Exclusion of chromosomal mosaicism: tables of 90%, 95% and 99% confidence limits and comments on use.

Tables specifically tailored to the exclusion of cytogenetic mosaicism at three confidence levels are presented. The consequences of the assumption of independence in application of the binomial theorem to this question are discussed. The tables are most applicable to the number of cells evaluated from cultures in which all mitoses are arrested in the first in vitro division. For long-term cultures the tables are conservatively applicable to the number of separate colonies evaluated. If n cells have been evaluated from phytohemagglutinin stimulated peripheral blood after 72 hr in cultures, the tables are applicable to between n/2 and n cells.

Chromosomes↗