A Simulation Study of Threats to Validity in Quasi-Experimental Designs: Interrelationship between Design, Measurement, and Analysis.

The Campbellian tradition provides a conceptual framework to assess threats to validity. On the other hand, different models of causal analysis have been developed to control estimation biases in different research designs. However, the link between design features, measurement issues, and concrete impact estimation analyses is weak. In order to provide an empirical solution to this problem, we use Structural Equation Modeling (SEM) as a first approximation to operationalize the analytical implications of threats to validity in quasi-experimental designs. Based on the analogies established between the Classical Test Theory (CTT) and causal analysis, we describe an empirical study based on SEM in which range restriction and statistical power have been simulated in two different models: (1) A multistate model in the control condition (pre-test); and (2) A single-trait-multistate model in the control condition (post-test), adding a new mediator latent exogenous (independent) variable that represents a threat to validity. Results show, empirically, how the differences between both the models could be partially or totally attributed to these threats. Therefore, SEM provides a useful tool to analyze the influence of potential threats to validity.

Factor structure of the Spanish version of the Life Orientation Test-Revised (LOT-R): Testing several models.

Studies of the dimensionality of the Life Orientation Test-Revised (LOT-R), considered as the gold standard in the measurement of dispositional optimism, yield controversial results due to the various factorial solutions found. Consequently, the factorial structure of the test has not yet been fully established. The aim of this study is to determine the factorial structure of the LOT-R by comparing seven previous models and their empirical evidence. The test was administered to 906 Spanish participants, ages 18 to 61 (mean age: 23; 56% males). Confirmatory factor analyses were conducted using polychoric correlations. Considering the theoretical background and the best model fit indices (RMSEA=.038; CFI=.98), we conclude that the test presents a factorial structure of a second-order factor (life orientation) composed of two factors (optimism and pessimism). Thus, we recommend using a single global score that could be referred to as life orientation but which ultimately represents the level of dispositional optimism.

Los estudios sobre la dimensionalidad del Test de Orientación Vital-Revisado (LOT-R), considerado el estándar en la medida del optimismo disposicional, resultan controvertidos al encontrar diversas soluciones factoriales. Así, no se ha establecido la estructura factorial definitiva de la prueba. El objetivo del presente estudio es determinar la estructura factorial del LOT-R mediante la comparación de los siete modelos empíricos existentes en la literatura. El instrumento fue administrado a 906 participantes españoles, de edades comprendidas entre los 18 y los 61 años (edad media = 23; 56% hombres). Se llevaron a cabo análisis factoriales confirmatorios sobre la matriz de correlaciones policóricas. Teniendo en cuenta los modelos teóricos existentes y los mejores índices de ajuste (RMSEA = 0,038; CFI = 0,98), concluimos que el LOT-R presenta una estructura factorial de segundo orden (orientación vital), compuesta por dos factores (Optimismo y Pesimismo). En consecuencia, recomendamos utilizar una única puntuación global que puede denominarse orientación vital y que, en último término, representa el nivel de optimismo disposicional.

Factor structure of the spanish version of the Life Orientation Test-Revised (LOT-R): testing several models / Estructura factorial de la versión española del Test de Orientación Vital-Revisado (LOT-R): comprobación de varios modelos

Studies of the dimensionality of the Life Orientation Test-Revised (LOT-R), considered as the gold standard in the measurement of dispositional optimism, yield controversial results due to the various factorial solutions found. Consequently, the factorial structure of the test has not yet been fully established. The aim of this study is to determine the factorial structure of the LOT-R by comparing seven previous models and their empirical evidence. The test was administered to 906 Spanish participants, ages 18 to 61 (mean age: 23; 56% males). Confirmatory factor analyses were conducted using polychoric correlations. Considering the theoretical background and the best model fit indices (RMSEA=.038; CFI=.98), we conclude that the test presents a factorial structure of a second-order factor (life orientation) composed of two factors (optimism and pessimism). Thus, we recommend using a single global score that could be referred to as life orientation but which ultimately represents the level of dispositional optimism (AU)

Los estudios sobre la dimensionalidad del Test de Orientación Vital-Revisado (LOT-R), considerado el estándar en la medida del optimismo disposicional, resultan controvertidos al encontrar diversas soluciones factoriales. Así, no se ha establecido la estructura factorial definitiva de la prueba. El objetivo del presente estudio es determinar la estructura factorial del LOT-R mediante la comparación de los siete modelos empíricos existentes en la literatura. El instrumento fue administrado a 906 participantes españoles, de edades comprendidas entre los 18 y los 61 años (edad media = 23; 56% hombres). Se llevaron a cabo análisis factoriales confirmatorios sobre la matriz de correlaciones policóricas. Teniendo en cuenta los modelos teóricos existentes y los mejores índices de ajuste (RMSEA = 0,038; CFI = 0,98), concluimos que el LOT-R presenta una estructura factorial de segundo orden (orientación vital), compuesta por dos factores (Optimismo y Pesimismo). En consecuencia, recomendamos utilizar una única puntuación global que puede denominarse orientación vital y que, en último término, representa el nivel de optimismo disposicional (AU)