Search results for "Regression analysis"

School fitness tests as predictors of adult health-related fitness.

2006

Relationships between adolescent physical fitness and adult health-related fitness were investigated. Forty-five subjects (20 males, 25 females) participated in physical fitness tests in 1976 and again in 2001. The adolescent physical fitness tests were distance running (2,000 m for boys or 1,500 m for girls), 50 m run, pull-ups (boys) or flexed arm hangs (girls), shuttle run, a 30-sec sit-up test, standing broad jump, hand grip-test, and sit-and-reach test. The adult health-related physical fitness index (APFI), stratified by sex, was formed by summing the z-scores of a bicycle ergometer test, sit-up test, hand-grip test, and sit-and-reach test. Height- and weight-adjusted correlations bet…

Structural invariants for the prediction of relative toxicities of polychloro dibenzo-p-dioxins and dibenzofurans

2004

Multivariate models are reported that can predict the relative toxicity of compounds with severe environmental impact, namely polychloro dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs). Multiple linear regression analysis (MLR) and partial least square projections of latent variables (PLS) show the usefulness of graph-theoretical descriptors, mainly topological charge indices (TCIs), in these series. The general trends of the group are correctly reproduced and better results are presented than have previously been published. In general, the more toxic compounds exhibit more symmetric molecular structures.

Assessing Frequency Domain Causality in Cardiovascular Time Series with Instantaneous Interactions

2009

Summary Background: The partial directed coherence (PDC) is commonly used to assess in the frequency domain the existence of causal relations between two time series measured in conjunction with a set of other time series. Although the multivariate autoregressive (MVAR) model traditionally used for PDC computation accounts only for lagged effects, instantaneous effects cannot be neglected in the analysis of cardiovascular time series. Objectives: We propose the utilization of an extended MVAR model for PDC computation, in order to improve the evaluation of frequency domain causality in the presence of zero-lag correlations among multivariate time series. Methods: A procedure for the identif…

On the internal multivariate quality control of analytical laboratories. A case study: the quality of drinking water

2001

Abstract Multivariate statistical process control (MSPC) tools, based on principal component analysis (PCA), partial least squares (PLS) regression and other regression models, are used in the present study for automatic detection of possible errors in the methods used for routine multiparametric analysis in order to design an internal Multivariate Analytical Quality Control (iMAQC) program. Such tools could notice possible failures in the analytical methods without resorting to any external reference since they use their own analytical results as a source for the diagnosis of the method's quality. Pseudo-univariate control charts provide an attractive alternative to traditional univariate …

Multivariate regression analysis applied to the calibration of equipment used in pig meat classification in Romania.

2016

This paper highlights the statistical methodology used in a dissection experiment carried out in Romania to calibrate and standardize two classification devices, OptiGrade PRO (OGP) and Fat-o-Meat'er (FOM). One hundred forty-five carcasses were measured using the two probes and dissected according to the European reference method. To derive prediction formulas for each device, multiple linear regression analysis was performed on the relationship between the reference lean meat percentage and the back fat and muscle thicknesses, using the ordinary least squares technique. The root mean squared error of prediction calculated using the leave-one-out cross validation met European Commission (EC…

2019

Objective A short questionnaire which can be applied for assessing patient satisfaction in different contexts and different countries is to be developed. Methods Six items addressing tangibles, reliability, responsiveness, assurance, empathy, and communication were analysed. The first five items stem from SERVQUAL (SERVice QUALity), the last stems from the discussion about SERVQUAL. The analyses were performed with data from 12 surveys conducted in six different countries (England, Finland, Germany, Greece, the Netherlands, Spain) covering two different conditions (type 2 diabetes, stroke). Sample sizes for included participants are 247 in England, 160 in Finland, 231 in Germany, 152 in Gre…

Prediction of chromatographic properties of organophosphorus insecticides by molecular connectivity

2000

A study is reported of the relationship between theR F values for a group of organophosphorus insecticides obtained by thin layer chromatography and a series of topological descriptors. By using multivariate regression, the corresponding connectivity functions were obtained, which had been selected on the basis of their respective statistical parameters: multiple correlation coefficient (r), standard error of estimate (s), F-Snedecor values and statistical significance (Student’s t). Regression analysis of the connectivity functions can predict the elution behaviour of any structurally similar derivative of this group of compounds with different stationary and mobile phases. Stability studi…

Surrogate Data Analysis for Assessing the Significance of the Coherence Function

2004

In cardiovascular variability analysis, the significance of the coupling between two time series is commonly assessed by setting a threshold level in the coherence function. While traditionally used statistical tests consider only the parameters of the adopted estimator, the required zero-coherence level may be affected by some features of the observed series. In this study, three procedures, based on the generation of surrogate series sharing given properties with the original but being structurally uncoupled, were considered: independent identically distributed (IID), Fourier transform (FT), and autoregressive (AR). IID surrogates maintained the distribution of the original series, while …

Influence of anti-inflammatory flavonoids on degranulation and arachidonic acid release in rat neutrophils.

1994

We assessed the effects of 24 flavonoid derivatives, reported as anti-inflammatory, on lysosomal enzyme secretion and arachidonic acid release in rat neutrophils. Amentoflavone, quercetagetin- 7-O -glucoside, apigenin, fisetin, kaem pferol, luteolin and quercetin were the most potent inhibitors of β-glucuronidase and lysozyme release. The first com pound was also able to inhibit basal release. These flavonoids besides chrysin and to a reduced extent, naringenin, significantly inhibited arachidonic acid release from membranes. A correlation between degranulation and arachidonic acid release was found for this series of compounds. Structureactivity relationships and implications for the anti-…

Association between biomarkers of inflammation and left ventricular hypertrophy in moderate chronic kidney disease.

2007

Aims: Left ventricular hyper- trophy (LVH) is a predictor for cardiovascu- lar mortality, and it is considered to be a surro- gate marker of preclinical cardiovascular dis- ease. This study aimed at evaluating whether fetuin-A plasma levels are decreased in pa- tients with moderate chronic kidney disease (CKD) and their linkage to plasma concentra- tions of hs-C-reactive protein (CRP), cardio- trophyn-1 (CT-1), tumor necrosis factor- (TNF-), propeptide of collagen Type I (PIP) and to LVH. Material and methods: We enrolled 64 moderate CKD and 55 essential hypertensives (EH) with normal renal func- tion as controls. All the patients underwent an echocardiographic examination; plasma sam- ples…