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Simultaneous Test (simultaneous + test)
Selected AbstractsDs -optimal designs for studying combinations of chemicals using multiple fixed-ratio ray experimentsENVIRONMETRICS, Issue 2 2005Michelle Casey Abstract Detecting and characterizing interactions among chemicals is an important environmental issue. Traditional factorial designs become infeasible as the number of compounds under study increases. Ray designs, which reduce the amount of experimental effort, can be considered when interest is restricted to relevant mixing ratios. Simultaneous tests for departure from additivity across multiple fixed-ratio rays in the presence and absence of single chemical data have been developed. Tests for characterizing interactions among subsets of chemicals at relevant mixing ratios have also been developed. Of primary importance are precise estimates for the parameters associated with these hypotheses. Since the hypotheses of interest are stated in terms of subsets of parameters, we have developed a methodology for finding Ds -optimal designs, which are associated with the minimum generalized variance of subsets of the parameter vector, along fixed-ratio rays. We illustrate these methods by characterizing the interactions of five organophosphorus pesticides (full-ray) as well as a subset of pesticides (reduced-ray) on a measure of motor activity. Copyright © 2004 John Wiley & Sons, Ltd. [source] A simultaneous test of unit root and level changeJOURNAL OF FORECASTING, Issue 3 2010Duk Bin Jun Abstract Testing the existence of unit root and/or level change is necessary in order to understand the underlying processes of time series. In many studies carried out so far, the focus was only on a single aspect of unit root and level change, therefore limiting a full assessment of the given problems. Our study aims to find a solution to the given problems by testing the two hypotheses simultaneously. We derive the likelihood ratio test statistic based on the state space model, and their distributions are created by the simulation method. The performance of the proposed method is validated by simulated time series and also applied to two Korean macroeconomic time series to confirm its practical application. This analysis can provide a solution to determine the underlying structure of arguable time series. Copyright © 2009 John Wiley & Sons, Ltd. [source] Jailed resources: conservation of resources theory as applied to burnout among prison guardsJOURNAL OF ORGANIZATIONAL BEHAVIOR, Issue 1 2007Jean-Pierre Neveu This study evaluates a salutogenic perspective of the burnout process. Building upon Hobfoll's (1989) Conservation of Resources theory, it proposes a simultaneous test of three hypothesized resources-based models. These competing models test the structure of burnout in relation to depleted resources (e.g., lack of skill utilization, of participation, of co-worker support, and of professional worth) and negative correlates (e.g., absenteeism and depression). SEM results provide equally good support for two resource-based models, although each of them proceeds from two different approaches (Leiter vs. Golembiewski). Of all burnout components, personal accomplishment is found to be least related to resources depletion, while emotional exhaustion is the most related to absenteeism and depression. Results are analyzed in light of existing literature and of the specific nature of the sample, a large population of French correctional officers (n,=,707). Implications for burnout theory and human resource management are discussed. Copyright © 2006 John Wiley & Sons, Ltd. [source] Revisiting Jablonski (1993): cladogenesis and range expansion explain latitudinal variation in taxonomic richnessJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 3 2007P. R. MARTIN Abstract The increase in diversity towards the equator arises from latitudinal variation in rates of cladogenesis, extinction, immigration and/or emigration of taxa. We tested the relative contribution of all four processes to the latitudinal gradient in 26 marine invertebrate orders with extensive fossil records, examined previously by David Jablonski. Coupling Jablonski's estimates of latitudinal variation in cladogenesis with new data on patterns of extinction and current distributions, we show that the present-day gradient in diversity is caused by higher rates of cladogenesis and subsequent range expansion (immigration) at lower latitudes. In contrast, extinction and emigration were not important in the creation of the latitudinal gradient in ordinal richness. This work represents one of the first simultaneous tests of the role of all four processes in the creation of the latitudinal gradient in taxonomic richness, and suggests that low tropical extinction rates are not essential to the creation of latitudinal diversity gradients. [source] | ||||||||||