Search results for "Main effect"

Uses of change-over designs and repeated measurements in sensory and consumer studies

1993

Abstract The paper illustrates two statistical methods, the design and analysis of sensory experiments taking into account the effects of serving order and previously assessed treatment and the analysis of experiments with time repeated measurements. Change-over design experiments balance both presentation order and carry-over effects. The proper analysis of variance allows the testing of these effects and the estimation of product means adjusted for carry-over effect. Repeated measurements occur when groups are being compared over time. Either a corrected split-plot or a multivariate analysis of variance (MANOVA) with measurements at different times forming the variable should be adopted t…

Comparison between Spanish young and elderly people evaluated using Rivermead Behavioural Memory Test

2010

The first objective of this work was to compare scores obtained in the daily memory function between young and elderly people, and to check whether there are differences between the groups for each of the profile scores obtained in the memory test. A second aim of this paper is to study the relationship between everyday memory and age, while controlling for gender and educational level. The total and profile scores obtained in the Rivermead Behavioural Memory Test were compared in a sample of 60 young and 120 elderly people from Valencia (Spain). Results showed significant differences between the two groups: those between 18 and 30 years obtained a higher average than those over 65. Once th…

Reliability and variability of bioimpedance measures in normal adults: Effects of age, gender, and body mass

2003

This study aimed to analyze the reliability and evaluate the causes of variability of bioimpedance parameters. Direct measures were analyzed because they are not affected by inappropriate prediction models. Resistance (R), reactance (Xc), and phase angle (PA) were determined at three fixed frequencies (5, 50, and 100 kHz) in 653 normal Germans (244 males and 409 females), aged 20-90 years, using a phase-sensitive whole-body tetrapolar bioimpedance analyzer (BIA 2000-M, Data Input, Germany). From these values, six bioimpedance ratios were calculated (R(5)/R(50), R(5)/R(100), Xc(5)/Xc(50), Xc(5)/Xc(100), PA(5)/PA(50), and PA(5)/PA(100)). Reliability of duplicate measurements, as determined by…

2013

Currently, a growing number of programs become available in statistical software for multiple imputation of missing values. Among others, two algorithms are mainly implemented: Expectation Maximization (EM) and Multiple Imputation by Chained Equations (MICE). They have been shown to work well in large samples or when only small proportions of missing data are to be imputed. However, some researchers have begun to impute large proportions of missing data or to apply the method to small samples. A simulation was performed using MICE on datasets with 50, 100 or 200 cases and four or eleven variables. A varying proportion of data (3% - 63%) was set as missing completely at random and subsequent…

Global sensitivity analysis of the SCOPE model : what drives simulated canopy - leaving sun - induced fluorescence?

2015

This study provides insight into the key variables that drive sun-induced chlorophyll fluorescence (SIF) emanating from vegetation canopies, based on a global sensitivity analysis (GSA) of the Soil-Canopy Observation of Photosynthesis and Energy (SCOPE) balance model. An updated version of the SCOPE model was used here (v1.53) which contains novel leaf physiological modules for determination of the steady state fluorescence yield: a photosynthesis model coupled with (a) submodels having empirically derived relationships, identified as TB12 for unstressed and TB12-D for drought conditions and (b) a mechanistic (MD12) submodel based on theoretical relationships. By inspecting Sobol's total or…

Use of response factorial design for process optimization of basic dye adsorption onto activated carbon derived from Persea species

2017

Abstract Full factorial design is a powerful and efficient mathematical approach widely applied in the optimization of response. The important parameters which affect the removal efficiency of methylene blue such temperature, initial pH of the solution, concentration and adsorbent dosage were optimized. They coded as A, B, C and D, consecutively, and were investigated at two levels (+ 1 and − 1). A linear mathematical model representing the influence of the different variables and their interactions was obtained. Main effect, Normal probability plot of residuals, analysis of variance (ANOVA), surface plots, and contour plots were used to study the effects and interaction effects between ope…

Maximin Model Robust Discrete Choice Experiments

2013

Discrete choice experiments have their genesis in conjoint analysis, which was based on first-order models. For this and other reasons, discrete choice experiments in practice are usually designed for estimation of main effects. In this paper, we explore the construction of maximin model robust designs when the experimenter is concerned about the presence of interactions. We consider three classes of models—main effects models, main effects models plus first-order interactions, and secondorder models, and we construct designs that maximize the minimum efficiency of the design for the three competing models. We do so first with standard linear models and then extend our analysis to nonlinear…

Shear and flexural strength prediction of corroded R.C. beams

2017

Abstract The purpose of the work was the study of the structural safety of R.C. beams subjected to corrosion processes though the derivation of moment-curvature diagrams and moment-to-shear interaction diagrams. Normal-strength reinforced concrete beams with longitudinal bars in the presence of transverse stirrups and subjected to corrosion processed are considered. Experimental results available in the literature related to corrosion processes, for steel bars, crack openings and bond degradation due to rust formation are reviewed. Then analytical laws relating to crack opening, bond degradation with attack penetration depth, through a rearranged form of Faraday’s law, are presented. An ana…

Master equation approach to the three-state open Majorana model

2019

The three-state Majorana model in the presence of dissipation is considered. Different models of system-environment interaction are explored, ranging from a situation where dissipation is the main effect to regimes where dephasing is mainly produced. It is shown that the detrimental effects of the noise are stronger in the presence of dissipation than in the presence of dephasing. The role of temperature is also discussed.

Development of Planning in Relation to Age, Attention, Simultaneous and Successive Processing

1994

This study investigated the development of planning and its relationship with age and other cognitive processes taken from the PASS model. Ninety-nine students in grades two, four, and eleven were administered planning, simultaneous processing, successive processing, and attention tasks. MANOVA with grade level and gender as independent variables revealed that grade level had a significant effect on planning, whereas gender did not. All but one planning variable showed a significant main effect of grade in subsequent ANOVAs. Pair-wise comparisons between grade levels indicated that the developmental trajectories were not uniform in different tasks. Regression analyses indicated that the co…