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Results for “statistical inference”

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At least 1,603 records · Page 89Linked to original sources
PubMed1975

Evaluating attitude change in community dental service programs in Minnesota, U.S.A.

Attitude changes of students participating in two community service programs at the University of Minnesota were evaluated using the semantic differential technique. Program I, a single day clinical experience at a state institution for the mentally retarded, involved 170 students; Program II, a 1-week clinical program in dental auxiliary utilization, involved 30 students. For each program, semantic differentials were designed to elicit scaled evauative responses toward concepts such as mental retardation and dentistry which were important to program objectives. Scales were administered in a pretest, post-test design. Statistically significant differences were noted for seven of eight target concepts, and appropriate attitude changes were inferred from these differences. Design of community programs and evaluation of desired attitude change using the semantic differential were discussed.

Attitude↗
PubMed1998

Relationship between diet, dental calculus and periodontal disease in domestic and feral cats in Australia.

OBJECTIVE: To compare the dental calculus scores and prevalence of periodontal disease in domestic cats eating commercially available canned and dry foods with those in feral cats consuming a diet consisting of small mammals, birds, reptiles and insects. ANIMALS: Twenty-nine feral cats and 20 domestic cats were included in the study. PROCEDURE: A dental chart and dental calculus scores were recorded using the maxillary canine, maxillary third and fourth premolar, mandibular canine, mandibular fourth premolar and first molar teeth on both sides. Periodontal disease was recorded using gingival recession, increased periodontal pocket formation, radiographic alveolar bone loss, osteomyelitis, furcation and root exposure, and the presence of calculus as indicators. RESULTS: Dental calculus scores were significantly higher in domestic cats than in feral cats. There was no statistical difference in the prevalence of periodontal disease between the two groups. CONCLUSIONS: It can be inferred that diet may play a role in the accumulation of calculus, but a diet based on live prey does not protect cats against periodontal disease.

Animal Feed↗
PubMed2004

Using overall allele-sharing to detect the presence of large-scale data errors and parameter misspecification in sib-pair linkage studies.

Data errors and marker allele frequency misspecification can lead to incorrect inference in linkage analysis. Here we demonstrate the effect of each on an allele-sharing statistic in a sample of sib pairs. In the context of relationship testing, we propose a new test that compares the sample genome-wide sib-pair allele sharing to its expectation and show that this test can detect the presence of large-scale data and model errors.

Alleles↗
PubMed1980

Pericardial rub in pericardial effusion: lack of correlation with amount of fluid.

The relation between the amount of pericardial fluid and the presence of a pericardial rub was examined in 76 patients with echocardiographic evidence of pericardial effusion. A pericardial rub was noted in 4 of 13 patients with small pericardial effusion (less than 100 ml), in 23 of 40 patients with moderate effusion (100 to 500 ml), and in ten of 23 patients with a large effusion. No difference in the amount of fluid was demonstrated in the group of patients with a rub when compared to the group without one. There was a statistically significant relation between the presence of a rub and the cause of the effusion. No inference as to the amount of pericardial fluid should be drawn from the presence or absence of a pericardial rub.

Child↗
PubMed2006

Phylogeny and genetic diversity of palolo worms (Palola, Eunicidae) from the tropical North Pacific and the Caribbean.

Palolo worms (Palola, Eunicidae) are best known for their annual mass spawnings, or "risings," in the South Pacific. Palola currently contains 14 morphologically similar species, mostly from shallow tropical waters. In this study, 60 specimens of Palola from nine locations in the tropical North Pacific and the Caribbean were sequenced for the two mitochondrial markers cytochrome c oxidase subunit I and 16S ribosomal RNA to infer phylogenetic relationships, genetic diversity, and phylogeography within the taxon. Phylogenetic analysis was performed using Bayesian statistics and parsimony. Vouchers of the same specimens were examined morphologically. Two major clades (A and B) can be distinguished within the monophyletic Palola. A number of individuals in clade B bear rows of ventral eyespots in the posterior body region, typical for swarming P. viridis and probably a synapomorphy for clade B. No morphological synapomorphy was found for clade A. Haplotypes from divergent clades often co-occur in the same location. Some haplotypes are geographically widespread, in one case covering the entire east-west expansion of the tropical Pacific. These results imply that despite the apparent absence of teleplanic larvae in eunicid polychaetes, long-distance dispersal is possible in at least some lineages of Palola. With the first taste of palolo I understood the Samoans' love for it. Certainly it suggested a salty caviar, but with something added, a strong, rich whiff of the mystery and fecundity of the ocean depths. -R. Steinberg. Pacific and Southeast Asian cooking. Time-Life Books, New York, 1970.

Animals↗
PubMed2000

[Mortality due to congenital malformations in Chile (1969-1997)].

BACKGROUND: Congenital malformations are defined as those structural, metabolic or functional defects found at birth. AIM: To study the mortality due to congenital malformations in Chile between 1969 and 1997, their type, individual, temporal and geographic variations. MATERIAL AND METHODS: A descriptive analysis of deaths registered by the National Statistics Institute and the Ministry of Health. Means, frequencies, raw and adjusted rates were calculated and inferences for some variables were carried out. RESULTS: Between 1969 and 1997 ther was tendency towards a reduction in rates of mortality due to congenital malformations and an increment in their relative importance. During the period, the risk for chromosome (98%) and osteomuscular (67%) malformations increased. Men and children of less than one year had the higher risk. In 1995, 1167 deaths due to congenital malformations were registered, 90% in children of less than 5 years. Higher risks occurred in urban zones (with a rate of 8.25 per 100,000) in the third region (rate 11.59) and second region (rate 11.2). Most deaths occurred in hospitals (85%). Main causes of death were circulatory system, central nervous system and chromosome malformations. CONCLUSIONS: The differences in regional deaths due to congenital malformations suggests specific risks that deserve further study.

Adolescent↗
PubMed2001

[Shear strength of bond of the dentin to GI-II glass-infiltrated alumia ceramic agter varying modes of surface conditioning].

OBJECTIVE: The adequate surface conditioning method for GI-II glass infiltrated alumia ceramic was investigated. METHODS: The test specimens were divided into 3 groups (A. HF + silicon, B. sandblasting + silicone and C. thermal silicoating + silicone). Shear bonding strengths of porcelain bonded to dentin were tested. RESULTS: The bond strength of group A and B slightly increased after one day but decreased sharply after 30 days. However, no statistical significance was observed. The group C showed a pronounced enlargement of bond strength after one day and had a durable bond after 30 days' thermal cycling. It is statistically significant when group C was compared with group A and B. CONCLUSION: It can be inferred that silicoating method be a better way for glass infiltrated alumia ceramic bonding.

Aluminum Oxide↗
PubMed1996

[The level of lipid peroxidation products in the plasma of patients with acute pancreatitis].

Plasma malondialdehyde level is studied in patients presenting acute pancreatitis. In those subjected to nonoperative treatment no statistically significant variations in MDA level, by comparison with the reference values, are registered. In patients undergoing surgery, a statistically significant increase in MDA, exceeding the uppermost limit of the reference values, is documented. The inference is reached that values above the reference ones (3.2 nmol/ml plasma) are usually interpreted as pointing to necrosis development in the pancreas.

Acute Disease↗
PubMed1997

Association of schistosomiasis with cervical cancer: detecting bias in clinical studies.

To investigate if Schistosoma haematobium infection increases the observed frequency of cervical cancer, data from literature were analysed in meta-analysis fashion. Results reveal that cervical cancer is statistically significantly less frequent in the presence of S. haematobium infection. A protective effect might be inferred; however, underlying bias in data collection and/or analysis is suspected. An approach to detecting bias is given, consisting of: (a) carefully stating and assessing the several components of the scientific method and; (b) identifying and contrasting the populations hypothesised and sampled. The approach is illustrated by searching for bias in the schistosomiasis-and-cancer reports. Sampling discrepancies were detected in patient geography, ages, and states of health, and suspected in disease prevalence sampled and disease prevalence reported. The conclusion is reached that effects of bias in the original studies preclude inference of a "protective" effect of S. haematobium infection against cervical cancer.

Africa↗
PubMedDate not supplied

Computational aspects of analysing random effects/longitudinal models.

Random effects and longitudinal models are becoming increasingly popular in the analysis of many types of data, including medical and biopharmaceutical, because of their richness and flexibility. They can be, however, difficult to fit using traditional statistical tools. Fortunately, there now exists a burgeoning collection of newer computational methods that can be applied to draw inferences with such models. This review attempts to provide an introduction to some of these techniques by describing them as extensions of the EM algorithm, currently a standard tool for the analysis of longitudinal and random effects models. For clarity of exposition, the extensions are classified into three types: large-sample iterative; large-sample simulation, and small-sample simulation.

Longitudinal Studies↗
PubMed2003

Manhattan world: orientation and outlier detection by Bayesian inference.

This letter argues that many visual scenes are based on a "Manhattan" three-dimensional grid that imposes regularities on the image statistics. We construct a Bayesian model that implements this assumption and estimates the viewer orientation relative to the Manhattan grid. For many images, these estimates are good approximations to the viewer orientation (as estimated manually by the authors). These estimates also make it easy to detect outlier structures that are unaligned to the grid. To determine the applicability of the Manhattan world model, we implement a null hypothesis model that assumes that the image statistics are independent of any three-dimensional scene structure. We then use the log-likelihood ratio test to determine whether an image satisfies the Manhattan world assumption. Our results show that if an image is estimated to be Manhattan, then the Bayesian model's estimates of viewer direction are almost always accurate (according to our manual estimates), and vice versa.

Artificial Intelligence↗
PubMed2000

Maternal antigen avoidance during pregnancy for preventing atopic disease in infants of women at high risk.

OBJECTIVES: To assess the effects of prescribing an antigen avoidance diet during pregnancy on the nutritional status of the mother and newborn and on the development of atopic disease in the child. The main focus is on women at high risk for giving birth to an atopic child, based on a history of atopic disease in the mother, father, or a previous child. SEARCH STRATEGY: The register of clinical trials maintained and updated by the Cochrane Pregnancy and Childbirth Group. SELECTION CRITERIA: All acceptably controlled comparisons of maternal antigen avoidance prescribed to pregnant women at high risk, regardless of the degree of antigen avoidance (number of foods eliminated from the diet) or the time of its onset during pregnancy. Data are also included on formula-fed (ie non-breastfed) infants in trials of maternal antigen avoidance intended to continue beyond pregnancy into the lactation period. DATA COLLECTION AND ANALYSIS: Data were extracted by the author from published reports, and supplemented by additional information from trialists contacted by the author. MAIN RESULTS: Three trials involving 504 women were included. Based on the single trial providing pertinent data, the restricted diet was associated with a small but statistically significant lower mean gestational weight gain (mean difference = -3.0% of prepregnancy weight) and a nonsignificantly higher risk of preterm birth. The combined evidence does not suggest a strong protective effect of maternal antigen avoidance on the incidence of atopic eczema or asthma during the first 12-18 months of life. Data on allergic rhinitis/conjuctivitis and urticaria are limited to a single trial each and are insufficient to draw meaningful inferences. Two trials suggest a lower incidence of skin prick tests to egg at 6 months of age, but the effect was no longer evident at 18 months, nor was any benefit apparent at either age for skin prick tests to milk. If anything, cord blood IgE levels were higher in the experimental (antigen avoidance) group. REVIEWER'S CONCLUSIONS: Prescription of an antigen avoidance diet to a high-risk woman during pregnancy is unlikely to reduce substantially her risk of giving birth to an atopic child. Moreover, such a diet may have an adverse effect on maternal and/or fetal nutrition.

Dietary Proteins↗
PubMed1997

Improvement of the power to detect complex disease genes by regional inference procedures.

Theoretical studies and simulations suggest that "true" linkage peaks are longer than "false" peaks of the same significance level. Our goal for this study was to improve the power of linkage detection by using a regional criterion for linkage; that is, requiring more than one p-value in a given region to pass a threshold. We tested this method by determining the power and type I error for finding the underlying loci on chromosomes 5 and 8 that contribute to the variability of Q1 (after adjusting Q1 for covariates). We used the Haseman-Elston sib-pair statistic to test for linkage of all 367 markers to the adjusted Q1 trait in 100 replicates. We compared the regional inference procedure to that of the Lander and Kruglyak (LK) criteria for significant and suggestive linkage. For example, the power to detect the chromosome 5 locus was 48% for the LK criterion for significant linkage (p < or = 0.0001) and 63% when we required two p-values out of five consecutive ones to be < or = 0.001. The type I error was not more than 5% for either method (2% for the LK and 5% for our criterion). This suggests that using a criterion based on length may improve the power of linkage detection for complex traits.

Chromosome Mapping↗
PubMed2004

Likelihood-based inference for the shape parameter of a two parameter Weibull distribution.

Based on a Type 2 censored sample, we use the likelihood-based approach to draw likelihood inference on the shape parameter gamma of a two-parameter Weibull distribution. In particular, we derive the profile, conditional and marginal likelihoods of gamma. Numerical results along with some concluding remarks regarding the use of likelihood-based methods for inference are provided.

Humans↗
PubMed2025

Common to rare transfer learning (CORAL) enables inference and prediction for a quarter million rare Malagasy arthropods.

DNA-based biodiversity surveys result in massive-scale data, including up to millions of species-of which, most are rare. Making the most of such data for inference and prediction requires modeling approaches that can relate species occurrences to environmental and spatial predictors, while incorporating information about their taxonomic or phylogenetic placement. Even if the scalability of joint species distribution models to large communities has greatly advanced, incorporating hundreds of thousands of species has not been feasible to date, leading to compromised analyses. Here we present a 'common to rare transfer learning' (CORAL) approach, based on borrowing information from the common species to enable statistically and computationally efficient modeling of both common and rare species. We illustrate that CORAL leads to much improved prediction and inference in the context of DNA metabarcoding data from Madagascar, comprising 255,188 arthropod species detected in 2,874 samples.

Animals↗
PubMed2002

Minimizing sample size when using exploratory factor analysis for measurement.

Traditional protocol for the determination of an adequate sample size is power analysis. Such a protocol is not useful when the primary hypothesis focuses on psychometric measurement properties. Traditional psychometrics advises that there should be 10 respondents per item. Both hypothetical and real research examples illustrate the usefulness of subsample analysis in determining that a sample size of at least 50 and not more than 100 subjects is adequate to represent and evaluate the psychometric properties of measures of social constructs. The "10 respondents per item" advice builds a sample size disincentive into the research design; it also represents "sample size overkill." Sample-size overkill occurs when the research design specifies a number of cases needed, which is in excess of the number actually needed for a desired inference.

Computer Simulation↗
PubMed2002

The advantage of functional prediction based on clustering of yeast genes and its correlation with non-sequence based classifications.

Sequence similarity is probably the most widely used tool to infer functional linkage between proteins. The fully sequenced, much researched, genome of Saccharomyces cerevisiae gives us on opportunity to compare and statistically quantify computational methods based on sequence similarity, which aim to detect such linkage. In addition, the amount of data regarding Saccharomyces Cerevisiae genes and proteins, which is not directly based on sequence is rapidly increasing. Consequently, it allows investigation of the connections and correlation between classification based on these types of data and that based solely on sequence similarity. In this work we start with a simple clustering algorithm to cluster genes based on the BLAST E-score of their similarity. We analyze how well one can infer function from these clusters and for how many of the genes that are currently unknown one can suggest a prediction. Given these parameters, we show that even a simple algorithm achieves better results than simply considering the BLAST output of matching genes. In the second part of the paper, we show that there is a highly significant correlation (p-value < 10(-4) for the vast majority of the experiments) between the aforementioned clusters and other types of classifications. Namely, we show that a pair of genes being clustered together is correlated with these genes having similar expression patterns in DNA array experiments and with the encoded proteins being involved in protein-protein interactions. Although this correlation is highly significant, it is, of course, not strong enough to be, by itself, a tool for predicting co-regulation of genes or interaction of proteins. We discuss possible explanations for this correlation. Furthermore, the statistical evaluation of these results should be considered when developing tools that are aimed at making such predictions.

Algorithms↗
PubMed2003

Systematic and statistical error in histogram-based free energy calculations.

A common technique for the numerical calculation of free energies involves estimation of the probability density along a given coordinate from a set of configurations generated via simulation. The process requires discretization of one or more reaction coordinates to generate a histogram from which the continuous probability density is inferred. We show that the finite size of the intervals used to construct the histogram leads to quantifiable systematic error. The width of these intervals also determines the statistical error in the free energy, and the choice of the appropriate interval is therefore driven by the need to balance the two sources of error. We present a method for the construction of the optimal histogram for a given system, and show that the use of this technique requires little additional computational expense. We demonstrate the efficacy of the technique for a model system, and discuss how the principles governing the choice of discretization interval could be used to improve extended sampling techniques.

Journal Article↗