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Squares Regression Analysis (square + regression_analysis)
Selected AbstractsThe Role of Cohabitation in RemarriageJOURNAL OF MARRIAGE AND FAMILY, Issue 2 2006Xiaohe Xu Using 3 subsamples of remarried respondents (n =1,583, 971, and 926) in the first wave of the National Survey of Families and Households, this study investigates how different types of cohabitation, especially postdivorce cohabitation, affect the timing and quality of remarriage in the United States. Ordinary Least Squares regression analysis indicates that postdivorce cohabitation in general and postdivorce cohabitation with multiple partners in particular delay remarriage. Furthermore, echoing previous research findings on the relationship between premarital cohabitation and relationship quality, the ordered logistic analysis shows that postdivorce cohabitation with a spouse is associated with lower levels of remarital happiness, and postdivorce cohabitation of all types tends to be associated with higher levels of remarital instability. Implications of these findings are briefly discussed. [source] Study of sensory properties of emollients used in cosmetics and their correlation with physicochemical propertiesINTERNATIONAL JOURNAL OF COSMETIC SCIENCE, Issue 6 2005M. E. Parente Eight liquid emollients (mineral oil, sunflower oil, squalane, decyl-oleate, isopropyl-myristate, octyldodecanol, dimethicone, and cyclomethicone) were characterized by instrumental and sensory methods and evaluated to determine the relationship between sensory and instrumental measures. Sensory analysis was carried out by a panel of 14 assessors, who evaluated the following attributes: difficulty of spreading, gloss, residue, stickiness, slipperiness, softness, and oiliness. The physicochemical properties measured were spreadability (at 1½ and 1 min), viscosity, and superficial tension. Data collected were statistically analysed by analysis of variance (ANOVA), principal component analysis (PCA), and linear partial least squares regression analysis (PLS). In consideration of their physicochemical characteristics, the studied emollients were sorted into three groups, in which the silicones distinctly separate from the rest. Sensory characteristics enabled the discrimination of four groups of emollients where, besides the two silicones, isopropyl myristate was also differentiated. PLS revealed that emollient sensory attributes could be well predicted by instrumental measurements. [source] Stacked partial least squares regression analysis for spectral calibration and predictionJOURNAL OF CHEMOMETRICS, Issue 10 2009Wangdong Ni Abstract Two novel algorithms which employ the idea of stacked generalization or stacked regression, stacked partial least squares (SPLS) and stacked moving-window partial least squares (SMWPLS) are reported in the present paper. The new algorithms establish parallel, conventional PLS models based on all intervals of a set of spectra to take advantage of the information from the whole spectrum by incorporating parallel models in a way to emphasize intervals highly related to the target property. It is theoretically and experimentally illustrated that the predictive ability of these two stacked methods combining all subsets or intervals of the whole spectrum is never poorer than that of a PLS model based only on the best interval. These two stacking algorithms generate more parsimonious regression models with better predictive power than conventional PLS, and perform best when the spectral information is neither isolated to a single, small region, nor spread uniformly over the response. A simulation data set is employed in this work not only to demonstrate this improvement, but also to demonstrate that stacked regressions have the potential capability of predicting property information from an outlier spectrum in the prediction set. Moisture, oil, protein and starch in Cargill corn samples have been successfully predicted by these new algorithms, as well as hydroxyl number for different instruments of terpolymer samples including and excluding an outlier spectrum. Copyright © 2009 John Wiley & Sons, Ltd. [source] Gender, socioeconomic status, need or access?AUSTRALIAN JOURNAL OF RURAL HEALTH, Issue 2 2009Differences in statin prescribing across urban, remote Australia, rural Abstract Objectives:,To assess differences in statin prescribing across Australia by geographic area. Design, setting and participants:,A cross-sectional study using Pharmaceutical Benefits Scheme data on statin prescribing by rurality, gender and patient postcode for the period May to December 2002. Participants were the Australian population, stratified by gender, quintile of index of relative socioeconomic disadvantage and rural, remote and metropolitan areas classification. Results:,Statin prescribing (scripts per 1000 population per month) was higher in urban areas (women, 51.915; men, 51.892) than in rural (women, 48.311; men, 48.098) or remote (women, 39.679; men, 34.145) areas. In urban areas, weighted least squares regression analysis showed a significant negative linear association between statin prescribing and socioeconomic status for both women (weighted least squares slope, ,3.358; standard error (SE) 0.057; P < 0.0001) and men (slope, ,0.507; SE 0.056; P < 0.0001). A similar association occurred in rural areas: women (slope, ,4.075; SE 0.122; P < 0.0001) and men (slope, ,3.455; SE 0.117; P < 0.0001), but not in remote areas where there was a positive linear association (slope, 3.120; SE 0.451; P < 0.0001) and men (slope, 3.098; SE 0.346; P < 0.0001). Conclusion:,Our results suggest differences in statin prescribing in Australia across geographic location, adjusting for age, gender and socioeconomic status. Implications:,These findings suggest that health inequalities due to geography should be addressed. [source] Biokinetic models for representing the complete inhibition of microbial activity at high substrate concentrationsBIOTECHNOLOGY & BIOENGINEERING, Issue 4 2001Gunaseelan Alagappan Abstract This paper reintroduces the Wayman and Tseng model for representing substrate inhibition effects on specific growth rate by further documenting its potential predictive capabilities. It also introduces a modification to this model in which an Andrews inhibition function is used in place of the Monod noninhibitory substrate function. This modification better represents the relationship between specific growth rate and substrate concentration for those substrates that show Andrews type inhibition at lower substrate concentrations, rather than the Monod type noninhibitory behavior described in the model of Wayman and Tseng. Results from nonlinear, least squares regression analysis are used to evaluate the ability of these models to empirically represent experimental data (both new and from the literature). The statistical goodness of fit is evaluated by comparing the regression results against those obtained using other empirical models. Finally, possible mechanisms of toxicity responsible for the observed inhibition trends are used to further justify use of these empirical models. The dominant mechanism considered to be relevant for conceptually explaining complete inhibition at high concentrations of solvents is the deterioration of cell membrane integrity. Literature citations are used to support this argument. This work should lead to improvements in the mathematical modeling of contaminant fate and transport in the environment and in the simulation of microbial growth and organic compound biodegradation in engineered systems. © 2001 John Wiley & Sons, Inc. Biotechnol Bioeng 75: 393,405, 2001. [source] Dizziness Presentations in U.S. Emergency Departments, 1995,2004ACADEMIC EMERGENCY MEDICINE, Issue 8 2008Kevin A. Kerber MD Abstract Objectives:, The objectives were to describe presentation characteristics and health care utilization information pertaining to dizziness presentations in U.S. emergency departments (EDs) from 1995 through 2004. Methods:, From the National Hospital Ambulatory Medical Care Survey (NHAMCS), patient visits to EDs for "vertigo-dizziness" were identified. Sample data were weighted to produce nationally representative estimates. Patient characteristics, diagnoses, and health care utilization information were obtained. Trends over time were assessed using weighted least squares regression analysis. Multivariable logistic regression analysis was used to control for the influence of age on the probability of a vertigo-dizziness visit during the study time period. Results:, Vertigo-dizziness presentations accounted for 2.5% (95% confidence interval [CI] = 2.4% to 2.6%) of all ED presentations during this 10-year period. From 1995 to 2004, the rate of visits for vertigo-dizziness increased by 37% and demonstrated a significant linear trend (p < 0.001). Even after adjusting for age (and other covariates), every increase in year was associated with increased odds of a vertigo-dizziness visit. At each visit, a median of 3.6 diagnostic or screening tests (95% CI = 3.2 to 4.1) were performed. Utilization of many tests increased over time (p < 0.01). The utilization of computerized tomography and magnetic resonance imaging (CT/MRI) increased 169% from 1995 to 2004, which was more than any other test. The rate of central nervous system diagnoses (e.g., cerebrovascular disease or brain tumor) did not increase over time. Conclusions:, In terms of number of visits and important utilization measures, the impact of dizziness presentations on EDs is substantial and increasing. CT/MRI utilization rates have increased more than any other test. [source] | ||||||||||