Correcting Measurement Error Bias in Interaction Models with Small Samples

Several methods have been suggested to estimate non-linear models with interaction terms in the presence of measurement error. Structural equation models eliminate measurement error bias, but require large samples. Ordinary least squares regression on summated scales, regression on factor scores and partial least squares are appropriate for small samples but do not correct measurement error bias. Two stage least squares regression does correct measurement error bias but the results strongly depend on the instrumental variable choice. This article discusses the old disattenuated regression method as an alternative for correcting measurement error in small samples. The method is extended to the case of interaction terms and is illustrated on a model that examines the interaction effect of innovation and style of use of budgets on business performance. Alternative reliability estimates that can be used to disattenuate the estimates are discussed. A comparison is made with the alternative methods. Methods that do not correct for measurement error bias perform very similarly and considerably worse than disattenuated regression

El reposo en agitación y el impulso de juego: algunas reflexiones sobre las teorías de B. Pascal y F. Schiller acerca del fracaso del proyecto humano

[spa] Revisar los Pensamientos de Pascal y las Cartas sobre la educación estética del hombre de Schiller constituye siempre un reto. Las teoríass de Pascal acerca del juego han sido analizadas fundamentalmente desde un punto de vista matemático, y pocas veces lo han sido desde un enfoque más antropológico y filosófico. El objetivo del presente artículo es reflexionar sobre sus papeles respectivos en la creación de un nuevo paradigma sobre el juego y leer cada uno de ellos a partir de las teorías del otro. Tal vez des este modo pueda probarse que ambos comparten un mismo proyecto irrealizable de lo humano. [eng] Reviewing the Thoughts by Pascal and the Letters on the Aesthetic Education of Man by Schiller is always a challenge. Pascal"s theories about play have been analyzed primarily from a mathematical point of view, and very few times have been examined from an anthropological and philosophical approach. The aim of this paper is to reflect on their respective roles in the creation of a new paradigm about play, and read each of them from the theories of the other. Perhaps in this way it might be proved that both share an unfeasible project about the human nature.

A peroxisomal glutathione transferase of Saccharomyces cerevisiae is functionally related to sulfur amino acid metabolism

Saccharomyces cerevisiae cells contain three omega-class glutathione transferases with glutaredoxin activity (Gto1, Gto2, and Gto3), in addition to two glutathione transferases (Gtt1 and Gtt2) not classifiable into standard classes. Gto1 is located at the peroxisomes, where it is targeted through a PTS1-type sequence, whereas Gto2 and Gto3 are in the cytosol. Among the GTO genes, GTO2 shows the strongest induction of expression by agents such as diamide, 1-chloro-2,4-dinitrobenzene, tert-butyl hydroperoxide or cadmium, in a manner that is dependent on transcriptional factors Yap1 and/or Msn2/4. Diamide and 1-chloro-2,4-dinitrobenzene (causing depletion of reduced glutathione) also induce expression of GTO1 over basal levels. Phenotypic analyses with single and multiple mutants in the S. cerevisiae glutathione transferase genes show that, in the absence of Gto1 and the two Gtt proteins, cells display increased sensitivity to cadmium. A gto1-null mutant also shows growth defects on oleic acid-based medium, which is indicative of abnormal peroxisomal functions, and altered expression of genes related to sulfur amino acid metabolism. As a consequence, growth of the gto1 mutant is delayed in growth medium without lysine, serine, or threonine, and the mutant cells have low levels of reduced glutathione. The role of Gto1 at the S. cerevisiae peroxisomes could be related to the redox regulation of the Str3 cystathionine -lyase protein. This protein is also located at the peroxisomes in S. cerevisiae, where it is involved in transulfuration of cysteine into homocysteine, and requires a conserved cysteine residue for its biological activity.