SEARCH · PubMed Health

Results for “data analysis”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

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

At least 577 records · Page 32Linked to original sources

PubMed1993

Exploratory data analysis in two-dimensional electrophoresis.

The use of computerized matching of proteins in the analysis of multiple two-dimensional electrophoresis (2DE) gels creates volumes of data that are readily accessible for exploratory analysis. When these data are used in health-effects studies or in studies to identify factors associated with particular diseases, hundreds or even thousands of hypotheses can be tested. Interpreting so many hypothesis tests requires some preliminary statistical evaluations of the data. In addition, prior to the preliminary statistical evaluations and subsequent hypothesis tests, accurate protein quantification and correct protein matching must be verified. In this report we present an approach used at the Centers for Disease Control to address these issues. This approach consists of a randomized experimental design incorporating replicate gels for each specimen, gel image analysis, protein matching, editing, Boolean unions of all gels to obtain correspondences and contradictions of match identification numbers, resolution of correspondences and contradictions, statistical tests to identify outliers, and finally an assessment of statistical and practical significance to focus attention on the proteins most likely to be associated with the effects under study. We illustrate our approach with data from an exploratory exposure-response study.

Blood Protein Electrophoresis↗

PubMed2000

Correlator beware: correlation has limited selectivity for fMRI data analysis.

Groups of time-courses created from fMRI data by the frequently used correlation analysis are often highly heterogeneous. This heterogeneity is due to the limited selectivity of correlation when trying to match brain time-courses to an externally imposed activation paradigm. Thus, this process unnecessarily generates many type I errors (false positives). Furthermore, as a consequence of the heterogeneity, time-courses identified and grouped by correlation may in fact describe different activations. After demonstrating this inadequacy, we give one particular approach to partition such a heterogeneous group into internally more homogeneous subgroups, using Kendall's coefficient of concordance W, and show its applicability and application to both simulated and in vivo data. Such group partition and "purification" will help subsequent inferential methods to deal more efficiently with false positives.

Algorithms↗

PubMed2003

Maximizing research opportunities: secondary data analysis.

Knowledge development in nursing can be enhanced by broadening the understanding of legitimate scientific inquiry. SDA uses existing data to answer research questions and can be especially useful for nurse researchers. Advantages of SDA include its potential for resource savings and its cost-effectiveness. Also, the investigator can circumvent data collection challenges such as finding appropriate participants. However, SDA does not require less rigor. A sound conceptualization of the research problem is still required, and identifying and obtaining appropriate data for SDA can be quite time-consuming. Nevertheless, SDA can be both a practical and appropriate research process that enables nurses to maximize their opportunities for answering important clinical questions.

Bias↗

PubMed2001

Web servlet-assisted, dial-in flow cytometry data analysis.

BACKGROUND: The obvious benefits of centralized data storage notwithstanding, the size of modern flow cytometry data files discourages their transmission over commonly used telephone modem connections. The proposed solution is to install at the central location a web servlet that can extract compact data arrays, of a form dependent on the requested display type, from the stored files and transmit them to a remote client computer program for display. METHODS: A client program and a web servlet, both written in the Java programming language, were designed to communicate over standard network connections. The client program creates familiar numerical and graphical display types and allows the creation of gates from combinations of user-defined regions. Data compression techniques further reduce transmission times for data arrays that are already much smaller than the data file itself. RESULTS: For typical data files, network transmission times were reduced more than 700-fold for extraction of one-dimensional (1-D) histograms, between 18 and 120-fold for 2-D histograms, and 6-fold for color-coded dot plots. Numerous display formats are possible without further access to the data file. CONCLUSIONS: This scheme enables telephone modem access to centrally stored data without restricting flexibility of display format or preventing comparisons with locally stored files.

Computer Communication Networks↗

PubMed2002

Rational addiction to alcohol: panel data analysis of liquor consumption.

Utilizing a panel data set of 42 states over the period 1959-1994, this paper estimates a rational addiction model for liquor consumption for the US. The empirical evidence is consistent with the rational addiction hypothesis proposed by Becker and Murphy. However, the results are sensitive to the assumption of homogeneity across states or over time.

Adult↗

PubMed2002

Parameter-extraction of a two-compartment model for whole-cell data analysis.

Neuronal modeling of patch-clamp data is based on approximations which are valid under specific assumptions regarding cell properties and morphology. Certain cells, which show a biexponential capacitance transient decay, can be modeled with a two-compartment model. However, for parameter-extraction in such a model, approximations are required regarding the relative sizes of the various model parameters. These approximations apply to certain cell types or experimental conditions and are not valid in the general case. In this paper, we present a general method for the extraction of the parameters in a two-compartment model without assumptions regarding the relative size of the parameters. All the passive electrical parameters of the two-compartment model are derived in terms of the available experimental data. The experimental data is obtained from a DC measurement (where the command potential is a hyperpolarizing DC voltage) and an AC measurement (where the command potential is a sinusoidal stimulus on a hyperpolarized DC potential) performed on the cell under test. Computer simulations are performed with a circuit simulator, XSPICE, to observe the effects of varying the two-compartment model parameters on the capacitive transients of the current response. Our general solution for the parameter-estimation of a two-compartment model may be used to model any neuron, which has a biexponential capacitive current decay. In addition, our model avoids the need for simplifying and perhaps erroneous approximations. Our equations may be easily implemented in hardware/software compensation schemes to correct the recorded currents for any series resistance or capacitive transient errors. Our general solution reduces to the results of previous researchers under their approximations.

Algorithms↗

PubMed1980

Interpretation of research data: exploratory data analysis.

The organization and presentation of research data is discussed, with emphasis on tabular arrays, frequency distributions, graphs, and diagrams. Data can be summarized by using various descriptive statistics, including mean, median, mode, range, variance, and standard deviation. Basic principles of data interpretation are reviewed, including how to handle regative results.

Data Collection↗

PubMedDate not supplied

Steady state enzyme kinetics: experimental design and data analysis by microcomputer.

One of the most time-consuming, yet essential, operations involved in the steady state kinetic study of enzymes is the design and optimization of experimental conditions. A computer program was developed for the Sinclair ZX-81 (or TS-1000, 1500) microcomputer which will optimize substrate concentration for preliminary and subsequently more refined kinetic analysis of one, two or three substrate systems. This program also analyzes the data collected from these studies by linear regression, weighted linear regression or weighted non-linear regression. In addition to the above program several of the enzyme kinetic statistical analysis programs of Cleland (1979) have been translated from FORTRAN into BASIC and implemented on the ZX-81 and the TRS-80 model II. Inexpensive commercially available software was used to overcome the inability of the ZX-81 to read data files from magnetic tape making the data analysis programs easier to use.

Computers↗

PubMed2006

Speciation of phosphorus fractionation in river sediments by explanatory data analysis.

This article investigates the controls on sediment phosphorus (P) speciation dynamics as a function of its fractionation into chemically defined operational pools along a river continuum. A total of 27 variables were analyzed in bed sediment samples collected for one year from six sampling points, along a 75km river continuum (Louros River, NW Greece). Multivariate explanatory analysis of the complex experimental data matrix was performed in order to unravel the spatial pattern of P speciation. Non-parametric examinations were also applied in order to elucidate the temporal variations encountered in the speciation of P. The results suggest that inorganic P species control P bioavailability in space and time. Organic P was found to be very reactive among the various fractions thus changing its bioavailability but exhibited no temporal variation. The utility of the proposed approach in the differentiation of natural and anthropogenic P inputs and their classification to point and non-point sources is demonstrated presenting a significant improvement compared to mere fractionation analysis.

Biological Availability↗

PubMed2000

Pk-fit: a pharmacokinetic/pharmacodynamic and statistical data analysis software.

This paper presents a new software, Pk-fit, to fit nonlinear models to kinetic and dynamic data. Directly connected to the spreadsheet, a statistical software component manager is available. In the data manager, Pk-fit includes the noncompartmental analysis module, the compartmental analysis module, the nonlinear kinetic process module, the drug absorption module, the pharmacodynamic data modeling module, the simultaneous fitting module, and the user-defined library module. In this paper, we present a detailed comparison of the kinetic analysis using Pk-fit and common software packages, PCNONLIN, MODFIT, MKMODEL, NONMEM, and SIPHAR, based on the textbook published by Gabrielsson in 1992, "Compilation of Analyzed Data Sets for Pharmacokinetic Software Evaluation." The comparison of Pk-fit with the reference softwares revealed that the parameters and their dispersion found with Pk-fit are consistent with the ones estimated with the other programs. In conclusion, Pk-fit constituted a valid tool for pharmacokinetic/pharmacodynamic data analysis.

Data Interpretation, Statistical↗

PubMedDate not supplied

Exploratory data analysis of the Mediterranean component of the BEEP programme.

Work Package 3 (WP3) uses the data generated by ecotoxicologists from 11 laboratories who sample twice per year at four sites (France, Italy, Spain and Greece) to conduct the Mediterranean portion of the BEEP programme (Biological Effects of Environmental Pollution in marine coastal ecosystems). The WP3 data have been compiled into files using a data base structure (one record=one measurement) that eases statistical analysis and importation of new data. Here we present our first attempt of exploratory analysis based on a subset of data from the campaigns in May and September of 2001 and 2002. For most biomarkers, data plot revealed a strong station*campaign interaction, confirmed by two-way ANOVAs. This could be "true" variability with biomarkers responding to contaminant inputs that have changed among the four sampling times. Alternatively it could betray analytical problems and inadequate sampling designs or a lack of stability in the biomarkers themselves whereby they change in random ways unrelated to environmental factors.

Acetylcholinesterase↗

PubMed1979

Some applications of categorical data analysis to epidemiological studies.

Several examples of categorized data from epidemiological studies are analyzed to illustrate that more informative analysis than tests of independence can be performed by fitting models. All of the analyses fit into a unified conceptual framework that can be performed by weighted least squares. The methods presented show how to calculate point estimate of parameters, asymptotic variances, and asymptotically valid chi 2 tests. The examples presented are analysis of relative risks estimated from several 2 x 2 tables, analysis of selected features of life tables, construction of synthetic life tables from cross-sectional studies, and analysis of dose-response curves.

Actuarial Analysis↗

PubMed2005

Police involvement in child protective services investigations: literature review and secondary data analysis.

This article examines the relationship of police and child protective services (CPS) coinvolvement to the outcomes of child maltreatment investigations. It reviews practice and empirical literature and conducts a secondary analysis of a national CPS data set. Most sources argue that coordination of the two agencies improves investigations and benefits children and families. Yet, sources also report friction between these agencies, interference with each other's job, and concerns that police involvement increases child removal. In the CPS case data, allegations were more likely to be judged credible when police also investigated and families were also more likely to receive various services. For neglect cases, multi-disciplinary decision making, but not police involvement per se, was linked to child removal. Across studies, police do not appear to hinder CPS effectiveness and may actually promote it. Their investigations should be coordinated in every community.

Child↗

PubMed1999

Data integration to assist gastric emptying data analysis.

The diagnosis of dyspepsia is very difficult because the symptoms are clinically aspecific and the gastric emptying time tests are of complex interpretation. An integrated and automated analysis of clinical and instrumental data may improve the diagnostic process. We present a system to collect data on dyspeptic patient from different sources which has been set up to assist the clinician in the diagnosis of dyspepsia. The data base integrates a wide set of symptoms with data coming from laboratory tests. Moreover, we assess the feasibility of classifying gastric emptying profiles using both octanoid acid excretion data and electrogastrography.

Adult↗

PubMed2000

Classification of human ovarian tumors using multivariate data analysis of polypeptide expression patterns.

Large amounts of data on quantitative gene expression are generated by procedures such as 2-DE analysis of proteins or cDNA microarrays. Quantitative molecular variation may potentially be used for the development of methods for the classification of tumors. We used here the statistical concepts of principal components analysis (PCA) and partial least square analysis (PLS) in an attempt to type ovarian tumors. Using a set of 170 polypeptides, 22 tumors were used to establish a model ("learning set") for classification into 3 groups (benign/borderline/malignant). Eighteen tumors were then used to test the model. Six of 8 carcinomas and 3 of 4 borderline tumors were correctly classified. Two of 6 benign lesions were correctly classified, 3 were classified as borderline and 1 as carcinoma. We conclude that it may be possible to classify tumors according to their constitutive protein expression profile using multivariate analysis, thus making classification by artificial intelligence a future possibility.

Breast Neoplasms↗

PubMed1997

Categorical data analysis in public health.

A greater variety of categorical data methods are used today than 15 years ago. This article surveys categorical data methods widely applied in public health research. Whereas large sample chi-square methods, logistic regression analysis, and weighted least squares modeling of repeated measures once comprised the primary analytic tools for categorical data problems, today's methodology is comprised of a much broader range of tools made available by increasing computational efficiency. These include computational algorithms for exact inference of small samples and sparsely distributed data, conditional logistic regression for modeling highly stratified data, and generalized estimating equations for cluster samples. The latter, in particular, has found wide use in modeling the marginal probabilities of correlated counted, binary, and multinomial outcomes. The various methods are illustrated with examples including a study of the prevalence of cerebral palsy in very low birthweight infants and a study of cancer screening in primary care settings.

Algorithms↗

PubMed1986

Real-time acquisition and data analysis of skeletal muscle contraction in a multi-user environment.

A data acquisition system is described which acquires data from contracting skeletal muscle. The system is designed to run in a multi-user environment while acquiring contractile data in real-time. Time dedicated solely to laboratory experiments is thus eliminated. A menu-driver is included to allow users to enter experimental commands with or without command arguments. Error monitoring functions prevent operator errors from causing data loss. Data storage in both ASCII and binary formats maximizes file flexibility, readability and accessibility. Finally, an on-line tutorial and help facility is provided for user training. The system developed is applicable to any experimental environment involving data acquisition, storage and analysis.

Animals↗

PubMed1991

[Computer-assisted data analysis of injuries of the skeletal system in polytrauma patients].

The data of 366 patients with multiple injuries were evaluated by application of data processing over a period of seven years. Age and sex distribution, location and combination of injuries, mortality, mechanism of accident, diagnostics as well as therapy were analysed. 91.3% of our patients had injuries of the skeleton. The male to female ratio was 2:1. In 55.4% the age of the patients ranged from 10 to 39 years. The mortality rate of all patients was 27.2%. In the third decade only 16.9% of the patients died. Whereas the mortality of the patients in the 1. decade as well as between the 7. and 9. decades of life was very high (33% and 50%). Most of the skeletal injuries were located in the shank (24% open fractures). The mortality rate increases with the number of injuries (Table III). Patients with concomitant injuries, such as head injuries and fractures of the extremities were the most common combination of multiple injuries. 20% of the patients in this group died. Patients with combined injuries of the head, chest, abdomen and skeleton had highest mortality (57%). X-ray examination of the skull, chest, extremities and mainly of the spine and pelvis should be subjects of routine diagnostics. In patients who were suspected of having a blunt abdominal trauma, the first diagnostic technique will be ultrasound. On account of the various number of concomitant injuries as well as the patients individuality, the estimation of prognosis by systems for the classification of the severity of injury is fraught with difficulties. The analysis of the evaluated data showed that previously small number of variables may predict the prognosis of the course of disease.

Adolescent↗