The Experts below are selected from a list of 306 Experts worldwide ranked by ideXlab platform
James Algina - One of the best experts on this subject based on the ideXlab platform.
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A Power Comparison of the Welch-James and Improved General Approximation Tests in the Split-Plot Design
Journal of Educational and Behavioral Statistics, 1998Co-Authors: James Algina, H. J. KeselmanAbstract:Power for the improved general approximation (IGA) and Welch-James (WJ) tests of the within-subjects (trials) main effect and the within-subjects x between-subjects (groups x trial) interaction was estimated for a Design with one between- and one within-subjects factor. The distribution of the data had two levels: multivariate normal and multivariate lognormal. Power estimates for conditions in which there were between-groups differences in dispersion matrices showed that, for both effects, there were conditions in which the IGA test was more powerful and conditions in which the WJ test was more powerful. The power advantage for the IGA test tended to be fairly small, whereas the power advantage for the WJ test was quite large in many conditions. Furthermore, the number of conditions favoring the WJ test was much larger than the number of conditions favoring the IGA test. Power for IGA, WJ, 9-adjusted, and MANOVA tests was compared for conditions in which dispersion matrices were equal across groups. Results indicate that little if any power was sacrificed by using WJ or IGA tests in place of MANOVA or i-adjusted tests. The Split-Plot Design with one between-subjects (groups) factor and one within-subjects (trials) factor is commonly used in educational and psychological research. The purpose of the research reported in this article was to compare the power of the multivariate Welch-James (WJ; H. J. Keselman, Carriere, & Lix, 1993) and improved general approximation (IGA; Algina, 1994; Huynh, 1978) tests. These tests were Designed to test the trials and the groups x trials effects when dispersion matrix equality is violated. Both the trials main effect and the groups x trials interaction can be tested by using univariate analysis of variance (ANOVA) or multivariate analysis of variance (MANOVA). The validity of these tests depends on the degree to which the data conform to the assumptions used in deriving the tests. Let J denote the number of levels in the groups factor, K the number of levels in the trials factor, and nj the number of subjects in level j of the groups factor, and let N = n, + - + nj. The data collected in the Design can be viewed as realizations of J random
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Generalization of Improved General Approximation tests to Split‐Plot Designs with multiple between‐subjects factors and/or multiple within‐subjects factors
British Journal of Mathematical and Statistical Psychology, 1997Co-Authors: James AlginaAbstract:Huynh developed the Improved General Approximation (IGA) tests of the between × within interaction and the within-subjects main effect in a Split-Plot Design with one within-subjects and one between-subjects factor. These tests were Designed to control the Type I error rate when multisample sphericity is violated. In Huynh's development the within-subjects main effect on weighted means is tested. Algina adapted the IGA test to test the within-subjects main effect on unweighted means in a Split-Plot Design with one within-subjects and one between-subjects factor. Both Huynh's original development and Algina's adaptation are generalized for use with repeated measures Designs with multiple between-subjects factors and/or multiple within-subjects factors. SAS/IML (SAS Institute Inc., 1989) modules for implementing the generalized test are made available.
Oluwatobi E. Bankole - One of the best experts on this subject based on the ideXlab platform.
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Effects of Cassava/Legumes Inter-cropping before Rice Season and Weeding Methods on Growth and Yields of Rice: Split-Plot Design Approach
International Journal of Ecological Economics and Statistics, 2016Co-Authors: Yisa Yakubu, A. U. Gbanguba, Oluwatobi E. BankoleAbstract:Lowland cereal cropping systems face shortages of nitrogen fertilizers, which are the most important nutrient limiting yields of cereals. Some studies have been carried out on the impact of preceding lowland rice cropping with cassava/legumes intercrop in the dry season on rice yields, in which the experimental treatments were arranged in a randomized complete block Design fashion. However, given the variety of problems posed by uncontrolled weed growth on crop yields, none of such studies have taken into proper consideration, the impact of weed-control method(s) used during experimentation on rice yield. A field study was undertaken to ascertain the effects of preceding lowland rice with cassava/legumes intercrop during dry season and that of weeding methods, on growth and yields of rice using a Split-Plot Design approach. The experiment was conducted on lowland experimental field of National Cereals Research Institute, Badeggi, in the Southern Guinea savanna zone of Nigeria during the 2013 cropping season. Seven intercropping systems (used as whole-Plot treatments), four weeding methods (used as subPlot treatments), and ten different rice parameters were used in the experiment, which was replicated three times. The results revealed that, for each parameter, the highest recorded rice yield was from the rice grown after intercropping Cassava with Aeschynomene legume followed by that grown after intercropping Cassava with Cowpea for every adopted weed-control method. For every intercropping system, the highest recorded rice yield was from the Plot subjected to the Two-hand weeding at 3 and 6 weeks after transplanting (WAT) followed by Herbicide at 3 WAT plus hand-weeding at 6 WAT for each parameter.
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effects of cassava legumes inter cropping before rice season and weeding methods on growth and yields of rice Split Plot Design approach
International Journal of Ecological Economics and Statistics, 2016Co-Authors: Yisa Yakubu, A. U. Gbanguba, Oluwatobi E. BankoleAbstract:Lowland cereal cropping systems face shortages of nitrogen fertilizers, which are the most important nutrient limiting yields of cereals. Some studies have been carried out on the impact of preceding lowland rice cropping with cassava/legumes intercrop in the dry season on rice yields, in which the experimental treatments were arranged in a randomized complete block Design fashion. However, given the variety of problems posed by uncontrolled weed growth on crop yields, none of such studies have taken into proper consideration, the impact of weed-control method(s) used during experimentation on rice yield. A field study was undertaken to ascertain the effects of preceding lowland rice with cassava/legumes intercrop during dry season and that of weeding methods, on growth and yields of rice using a Split-Plot Design approach. The experiment was conducted on lowland experimental field of National Cereals Research Institute, Badeggi, in the Southern Guinea savanna zone of Nigeria during the 2013 cropping season. Seven intercropping systems (used as whole-Plot treatments), four weeding methods (used as subPlot treatments), and ten different rice parameters were used in the experiment, which was replicated three times. The results revealed that, for each parameter, the highest recorded rice yield was from the rice grown after intercropping Cassava with Aeschynomene legume followed by that grown after intercropping Cassava with Cowpea for every adopted weed-control method. For every intercropping system, the highest recorded rice yield was from the Plot subjected to the Two-hand weeding at 3 and 6 weeks after transplanting (WAT) followed by Herbicide at 3 WAT plus hand-weeding at 6 WAT for each parameter.
Roy Edward Bruns - One of the best experts on this subject based on the ideXlab platform.
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Split-Plot Designs and normal probability graphs for the optimization of chemical systems
Analytica Chimica Acta, 2005Co-Authors: João Alexandre Bortoloti, Cleber N. Borges, Roy Edward BrunsAbstract:Abstract An approximate procedure based on normal probability graphs for selecting significant parameters of models calculated from the results of Split-Plot Designs is proposed. Its application can result in a substantial reduction in the number of experiments that need to be performed. The method is applied to three Split-Plot Design results for real data reported in the literature: (1) three plasticizer mixture components with different extrusion rates and drying temperatures, (2) three fish pattie ingredients at different cooking and frying temperature and times and (3) Cr(VI) catalytic determinations employing three reagents of varying concentrations and three solvent components of varying proportions. Approximate models determined from the proposed procedure are compared with those determined using complete Split-Plot ANOVA analyses. The robustness of the procedure is tested for one of the Split-Plot Design results using replication, main-Plot error and sub-Plot error variance estimates that change according to a 2 3 factorial Design.
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Split-Plot Design optimization for trace determination of lead by anodic stripping voltammetry in a homogeneous ternary solvent system
Chemometrics and Intelligent Laboratory Systems, 2004Co-Authors: João Alexandre Bortoloti, Roy Edward Bruns, João Carlos De Andrade, Raimundo Kennedy VieiraAbstract:Abstract A Split-Plot Design has been used to simultaneously optimize reagent conditions and solvent medium for Pb2+ determination by anodic stripping voltammetry (ASV). Three mixture components, N,N-dimethylformamide (DMF), ethanol and water, and two process variable levels, ammonium acetate (supporting electrolyte) and hydrochloric acid concentrations, were varied. The calculations of main-Plot, subPlot and main-subPlot interaction ANOVA sums of squares for regression and lack of fit are illustrated. These values are shown to be useful for model development. Six different models were evaluated. The bilinear-special cubic model has only a very slight lack of fit and is preferred. Standard error estimates were calculated using a method described in the literature by Cornell, and approximate critical values for t-tests on the model coefficients were investigated. Normal probability graphs seem appropriate for this analysis. The significant terms in this model are capable of describing how the mixture response surfaces change as process level conditions are varied. Optimized mixture proportions for each factorial Design level are determined. Optimum conditions in the (− −) main-Plot quadrant for the determination of lead by ASV in the homogeneous ternary solvent system were achieved with a solvent composition of 8.0 g of N,N-dimethylformamide (DMF), 7.0 g of ethanol and 5.0 g of water, corresponding to 40% m/m of DMF, 35% n/m of ethanol and 25% m/m of water. Water is essential since the sample and the buffer (0.1 mol kg−1 ammonium acetate containing 0.00880 mol kg−1 HCl) are added to the system as aqueous solutions. The other three main-Plot quadrants presented optimum analytical signals for 95% aqueous solutions. The Split-Plot Design seems to be especially appropriate for simultaneously optimizing process and mixture variables of this chemical system facilitating operational procedures by means of block randomization.
João Alexandre Bortoloti - One of the best experts on this subject based on the ideXlab platform.
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Split-Plot Designs and normal probability graphs for the optimization of chemical systems
Analytica Chimica Acta, 2005Co-Authors: João Alexandre Bortoloti, Cleber N. Borges, Roy Edward BrunsAbstract:Abstract An approximate procedure based on normal probability graphs for selecting significant parameters of models calculated from the results of Split-Plot Designs is proposed. Its application can result in a substantial reduction in the number of experiments that need to be performed. The method is applied to three Split-Plot Design results for real data reported in the literature: (1) three plasticizer mixture components with different extrusion rates and drying temperatures, (2) three fish pattie ingredients at different cooking and frying temperature and times and (3) Cr(VI) catalytic determinations employing three reagents of varying concentrations and three solvent components of varying proportions. Approximate models determined from the proposed procedure are compared with those determined using complete Split-Plot ANOVA analyses. The robustness of the procedure is tested for one of the Split-Plot Design results using replication, main-Plot error and sub-Plot error variance estimates that change according to a 2 3 factorial Design.
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Split-Plot Design optimization for trace determination of lead by anodic stripping voltammetry in a homogeneous ternary solvent system
Chemometrics and Intelligent Laboratory Systems, 2004Co-Authors: João Alexandre Bortoloti, Roy Edward Bruns, João Carlos De Andrade, Raimundo Kennedy VieiraAbstract:Abstract A Split-Plot Design has been used to simultaneously optimize reagent conditions and solvent medium for Pb2+ determination by anodic stripping voltammetry (ASV). Three mixture components, N,N-dimethylformamide (DMF), ethanol and water, and two process variable levels, ammonium acetate (supporting electrolyte) and hydrochloric acid concentrations, were varied. The calculations of main-Plot, subPlot and main-subPlot interaction ANOVA sums of squares for regression and lack of fit are illustrated. These values are shown to be useful for model development. Six different models were evaluated. The bilinear-special cubic model has only a very slight lack of fit and is preferred. Standard error estimates were calculated using a method described in the literature by Cornell, and approximate critical values for t-tests on the model coefficients were investigated. Normal probability graphs seem appropriate for this analysis. The significant terms in this model are capable of describing how the mixture response surfaces change as process level conditions are varied. Optimized mixture proportions for each factorial Design level are determined. Optimum conditions in the (− −) main-Plot quadrant for the determination of lead by ASV in the homogeneous ternary solvent system were achieved with a solvent composition of 8.0 g of N,N-dimethylformamide (DMF), 7.0 g of ethanol and 5.0 g of water, corresponding to 40% m/m of DMF, 35% n/m of ethanol and 25% m/m of water. Water is essential since the sample and the buffer (0.1 mol kg−1 ammonium acetate containing 0.00880 mol kg−1 HCl) are added to the system as aqueous solutions. The other three main-Plot quadrants presented optimum analytical signals for 95% aqueous solutions. The Split-Plot Design seems to be especially appropriate for simultaneously optimizing process and mixture variables of this chemical system facilitating operational procedures by means of block randomization.
Yisa Yakubu - One of the best experts on this subject based on the ideXlab platform.
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Effects of Cassava/Legumes Inter-cropping before Rice Season and Weeding Methods on Growth and Yields of Rice: Split-Plot Design Approach
International Journal of Ecological Economics and Statistics, 2016Co-Authors: Yisa Yakubu, A. U. Gbanguba, Oluwatobi E. BankoleAbstract:Lowland cereal cropping systems face shortages of nitrogen fertilizers, which are the most important nutrient limiting yields of cereals. Some studies have been carried out on the impact of preceding lowland rice cropping with cassava/legumes intercrop in the dry season on rice yields, in which the experimental treatments were arranged in a randomized complete block Design fashion. However, given the variety of problems posed by uncontrolled weed growth on crop yields, none of such studies have taken into proper consideration, the impact of weed-control method(s) used during experimentation on rice yield. A field study was undertaken to ascertain the effects of preceding lowland rice with cassava/legumes intercrop during dry season and that of weeding methods, on growth and yields of rice using a Split-Plot Design approach. The experiment was conducted on lowland experimental field of National Cereals Research Institute, Badeggi, in the Southern Guinea savanna zone of Nigeria during the 2013 cropping season. Seven intercropping systems (used as whole-Plot treatments), four weeding methods (used as subPlot treatments), and ten different rice parameters were used in the experiment, which was replicated three times. The results revealed that, for each parameter, the highest recorded rice yield was from the rice grown after intercropping Cassava with Aeschynomene legume followed by that grown after intercropping Cassava with Cowpea for every adopted weed-control method. For every intercropping system, the highest recorded rice yield was from the Plot subjected to the Two-hand weeding at 3 and 6 weeks after transplanting (WAT) followed by Herbicide at 3 WAT plus hand-weeding at 6 WAT for each parameter.
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effects of cassava legumes inter cropping before rice season and weeding methods on growth and yields of rice Split Plot Design approach
International Journal of Ecological Economics and Statistics, 2016Co-Authors: Yisa Yakubu, A. U. Gbanguba, Oluwatobi E. BankoleAbstract:Lowland cereal cropping systems face shortages of nitrogen fertilizers, which are the most important nutrient limiting yields of cereals. Some studies have been carried out on the impact of preceding lowland rice cropping with cassava/legumes intercrop in the dry season on rice yields, in which the experimental treatments were arranged in a randomized complete block Design fashion. However, given the variety of problems posed by uncontrolled weed growth on crop yields, none of such studies have taken into proper consideration, the impact of weed-control method(s) used during experimentation on rice yield. A field study was undertaken to ascertain the effects of preceding lowland rice with cassava/legumes intercrop during dry season and that of weeding methods, on growth and yields of rice using a Split-Plot Design approach. The experiment was conducted on lowland experimental field of National Cereals Research Institute, Badeggi, in the Southern Guinea savanna zone of Nigeria during the 2013 cropping season. Seven intercropping systems (used as whole-Plot treatments), four weeding methods (used as subPlot treatments), and ten different rice parameters were used in the experiment, which was replicated three times. The results revealed that, for each parameter, the highest recorded rice yield was from the rice grown after intercropping Cassava with Aeschynomene legume followed by that grown after intercropping Cassava with Cowpea for every adopted weed-control method. For every intercropping system, the highest recorded rice yield was from the Plot subjected to the Two-hand weeding at 3 and 6 weeks after transplanting (WAT) followed by Herbicide at 3 WAT plus hand-weeding at 6 WAT for each parameter.