Optimal number of strata for the stratified methods in computerized adaptive testing

Test security can be a major problem in computerized adaptive testing, as examinees can share information about the items they receive. Of the different item selection rules proposed to alleviate this risk, stratified methods are among those that have received most attention. In these methods, only low discriminative items can be presented at the beginning of the test and the mean information of the items increases as the test goes on. To do so, the item bank must be divided into several strata according to the information of the items. To date, there is no clear guidance about the optimal number of strata into which the item bank should be split. In this study, we will simulate conditions with different numbers of strata, from 1 (no stratification) to a number of strata equal to test length (maximum level of stratification) while manipulating the maximum exposure rate that no item should surpass (rmax) in its whole domain. In this way, we can plot the relation between test security and accuracy, making it possible to determine the number of strata that leads to better security while holding constant measurement accuracy. Our data indicates that the best option is to stratify into as many strata as possible.This research was supported by a grant from the Spanish Ministerio de Ciencia e Innovación (project number PSI2009–10341), and by a grant from the Fundación Universitaria Antonio Gargallo and the Obra Social de Ibercaja

Influence of vulnerability factors in panic disorder severity

Background: We studied herein the predictive value for panic severity of three well-based vulnerability factors: personality traits (neuroticism and extraversion; NEO-PI-R), anxiety sensitivity (ASI), and perceived control (ACQ-R). Method: The sample was composed of 52 participants diagnosed with panic disorder, with or without agoraphobia, according to DSM-IV-TR criteria. Results: Our results revealed that the anxiety facet is a better predictor of panic severity than neuroticism. Anxiety sensitivity increases the predictive value for panic severity and, finally, perception of control of emotions is the only perception control subscale that increases the predictive value for panic severity more than the anxiety facet and anxiety sensitivity. Conclusions: This finding supports the assumption of the importance of taking into account the assessment of the lower order dimensions of the vulnerability factors in the field of psychopathology studies. Furthermore, the predictive value of perception of control of emotions indicates the importance of this specific vulnerability factor in the etiology of panic disorder (with or without agoraphobia) and, thus, shows the necessity to include emotion regulation strategies in the psychological treatments.Influencia de factores de vulnerabilidad en la gravedad del trastorno de pánico. Antecedentes: en este trabajo se estudia el valor predictivo sobre la gravedad del pánico de tres factores de vulnerabilidad bien establecidos: rasgos de personalidad (neuroticismo y extraversión; NEOPI-R), sensibilidad a la ansiedad (ASI) y percepción de control (ACQ-R). Método: la muestra fue de 52 participantes con diagnóstico de trastorno de pánico, con o sin agorafobia, según criterios DSM-IV-TR. Resultados: nuestros resultados revelan que la faceta de ansiedad es mejor predictor de la gravedad del pánico que el neuroticismo. La sensibilidad a la ansiedad aumenta el valor predictivo sobre la gravedad del pánico y, finalmente, la percepción de control de las emociones es la única subescala de la percepción de control que aumenta la capacidad predictiva más allá de la faceta de ansiedad y la sensibilidad a la ansiedad. Conclusiones: estos resultados apoyan el supuesto sobre la importancia de evaluar las dimensiones de orden inferior de los factores de vulnerabilidad en los estudios psicopatológicos. Además, el valor predictivo de la percepción de control de las emociones indica la importancia de este factor específico de vulnerabilidad en la etiología del trastorno de pánico (con o sin agorafobia) lo que muestra la necesidad de incluir estrategias de regulación emocional en los tratamientos psicológicos.Funded by Gobierno de Aragón (Dpto. Industria e Innovación), Fondo Social Europeo and Ministerio de Economía y Competitividad (Spain), Plan Nacional (PSI2010-21423/PSIC)

eCat-Listening: diseño y propiedades psicométricas de un test adaptativo informatizado de comprensión auditiva de la lengua inglesa

In this study, eCAT-Listening, a new computerized adaptive test for the evaluation of English Listening, is described. Item bank development, anchor design for data collection, and the study of the psychometric properties of the item bank and the adaptive test are described. The calibration sample comprised 1.576 participants. Good psychometric guarantees: the bank is unidimensional, the items are satisfactorily fi tted to the 3-parameter logistic model, and an accurate estimation of the trait level is obtained. As validity evidence, a high correlation was obtained between the estimated trait level and a latent factor made up of the diverse criteria selected. The analysis of the trait level estimation by means of a simulation led us to fi x the test length at 20 items, with a maximum exposure rate of .40En este trabajo se describe eCAT-Listening, un nuevo test adaptativo informatizado para la medición del nivel de comprensión auditiva del inglés. Se describe la elaboración del banco de ítems, el diseño de anclaje para la recogida de datos y el estudio de las propiedades psicométricas del banco de ítems y del test adaptativo. La muestra de calibración fue de 1.576 personas. Se obtienen unas buenas garantías psicométricas: el banco es unidimensional, los ítems se ajustan satisfactoriamente al modelo logístico de 3 parámetros y se consigue una estimación precisa de los diferentes niveles de rasgo. Como prueba de validez, se obtuvo una alta correlación entre el rasgo estimado y un factor latente de nivel de inglés compuesto por las diferentes puntuaciones criterio utilizadas en el estudio. El análisis de la estimación del nivel de rasgo mediante simulación nos lleva a fijar la longitud del test adaptivo en 20 ítems, con una tasa máxima de exposición de 0,40This research was supported by two grants from the Spanish Ministry of Science and Innovation (project numbers PSI2009-10341 and PSI2008-01685) and by the UAM-IIC Chair «Psychometric Models and Applications

Computerized adaptive testing: the capitalization on chance problem

This paper describes several simulation studies that examine the effects of capitalization on chance in the selection of items and the ability estimation in CAT, employing the 3-parameter logistic model. In order to generate different estimation errors for the item parameters, the calibration sample size was manipulated (! = 500, 1000 and 2000 subjects) as was the ratio of item bank size to test length (banks of 197 and 788 items, test lengths of 20 and 40 items), both in a CAT and in a random test. Results show that capitalization on chance is particularly serious in CAT, as revealed by the large positive bias found in the small sample calibration conditions. For broad ranges of θ, the overestimation of the precision (asymptotic Se) reaches levels of 40%, something that does not occur with the RMSE (θ). The problem is greater as the item bank size to test length ratio increases. Potential solutions were tested in a second study, where two exposure control methods were incorporated into the item selection algorithm. Some alternative solutions are discussed.This research was partly supported by two grants from the Spanish Ministerio de Educación y Ciencia (projects PSI2008-01685 and PSI2009-10341) and by the UAM-IIC Chair Psychometric Models and Applications

Item parameter drift in computerized adaptive testing: study with eCAT

En el presente trabajo se muestra el análisis realizado sobre un Test Adaptativo Informatizado (TAI) diseñado para la evaluación del nivel de inglés, denominado eCAT, con el objetivo de estudiar el deterioro de parámetros (parameter drift) producido desde la calibración inicial del banco de ítems. Se ha comparado la calibración original desarrollada para la puesta en servicio del TAI (N= 3224) y la calibración actual obtenida con las aplicaciones reales del TAI (N= 7254). Se ha analizado el Funcionamiento Diferencial de los Ítems (FDI) en función de los parámetros utilizados y se ha simulado el impacto que sobre el nivel de rasgo estimado tiene la variación en los parámetros. Los resultados muestran que se produce especialmente un deterioro de los parámetros a y c, que hay un importante número de ítems del banco para los que existe FDI y que la variación de los parámetros produce un impacto moderado en la estimación de θ de los evaluados con nivel de inglés alto. Se concluye que los parámetros de los ítems se han deteriorado y deben ser actualizadosThis study describes the parameter drift analysis conducted on eCAT (a Computerized Adaptive Test to assess the written English level of Spanish speakers). The original calibration of the item bank (N = 3224) was compared to a new calibration obtained from the data provided by most eCAT operative administrations (N = 7254). A Differential Item Functioning (DIF) study was conducted between the original and the new calibrations. The impact that the new parameters have on the trait level estimates was obtained by simulation. Results show that parameter drift is found especially for a and c parameters, an important number of bank items show DIF, and the parameter change has a moderate impact on high-level-English θ estimates. It is then recommended to replace the original estimates by the new se

Reproductive Behavior of Zebu and 5/8 Zebu x 3/8 Simmental Genotypes in Central Cuba Locations

The aim of this paper was to evaluate the reproductive behavior of female Zebu and 5/8 Zebu x 3/8 Simmental on a genetic farm in the central region of Cuba. The research was made between 2010 and 2014. The individual records of 255 cows; 200 Zebus (106 white and 94 bermeja) and 55 crossbreds (5/8 Zebu x 3/8 Simmental) were included. The calving-first insemination interval (CFII), calving-gestation interval (SP), inter-calving period (CCI), and service per gestation (S/G) were calculated. Besides, the effects of genotype, parity, quarter and calving year were evaluated using the above indicators. The descriptive statistics were estimated, and a general linear model was used to determine the effects of each variation source. The three genotypes showed low reproductive efficiency, though slightly more favorable for 5/8 Zebu x 3/8 Simmental. The CFII, SP, and CCI were influenced (P <0.05) by the calving year, genotype, and parity, whereas SP was influenced by the calving quarter only (P <0.05). The gestation service was not affected by any factor. It was concluded that the three genotypes studied underwent severe deterioration of reproductive indicators, influenced by the genotype, quarter, calving year, and parity

Estudio de mejora en los sistemas de comunicación de mando y control en unidades de infantería ligero protegida en zona urbanizada.

La evolución de los conflictos armados a lo largo de toda la historia exige a los medios tecnológicos una permanente adaptación y renovación. En la actualidad, los ambientes urbanos cobran una gran importancia en el estudio de escenarios de conflictos posibles debido a factores muy influyentes como la sobrepoblación, el cambio climático o las masivas migraciones a ciudades. La adaptación de nuestras Fuerzas Armadas tanto a este escenario como al combate que se desarrolla en el mismo, es indispensable para lograr poseer en el futuro un Ejército moderno y polivalente. A través del plan “FUERZA 2035”, el Jefe del Estado Mayor del Ejército de Tierra pretende, mediante una planificación, constituir para 2035 fuerzas operativas flexibles y cohesionadas, capaces de operar en cualquier estructura multinacional y poseedoras de medios tecnológicos avanzados que se constituyan como una herramienta indispensable para el despliegue en escenarios potencialmente probables, como entornos urbanos.Siendo las unidades de infantería ligero protegidas las idóneas para desplegar en este escenario debido a cualidades como su potencia de fuego, su flexibilidad y su movilidad combinando elementos a pie con vehículos ligero protegidos; deben estas tener en disposición sistemas tecnológicos de comunicación que permitan a los jefes de las distintas unidades ejercer la función de mando y control de una manera eficaz y óptima, siendo conscientes de la peculiaridad y compartimentación del terreno urbano. El mando y control se concibe como el ejercicio de la autoridad y dirección, por un mando específico designado para ello, sobre las fuerzas que les han sido asignadas para el cumplimiento de la misión. Esta función fundamental se realiza a través de conjuntos de elementos interrelacionados que desarrollan las acciones necesarias para proporcionar al mando, en tiempo útil, el conocimiento de la situación, constituyendo el soporte necesario para la toma de decisiones, la transmisión de órdenes y el control de su ejecución. Por ello, el objetivo de este trabajo es proponer un sistema de comunicación que permita a los Jefes de Compañía y Sección de Unidades de infantería ligero protegidas ejercer un adecuado mando y control de sus elementos, tanto vehiculares como combatientes a pie, en zonas urbanizadas. Para alcanzar este objetivo, se ha seguido una metodología de trabajo articulada en cuatro fases definidas. En primer lugar, se han extraído las necesidades de mando y control de unidades de infantería ligero protegidas en zonas urbanizadas y se han determinación las debilidades que presentan los sistemas de comunicación que se emplean en la actualidad. A continuación, se han estudiado las soluciones tecnológicas que permiten resolver potencialmente dichas necesidades. Por último, tras el análisis y comparación de las ventajas y limitaciones de los sistemas propuestos, se ha procedido a identificar los pasos que serían necesarios llevar a cabo para lograr la implementación de la solución seleccionada en las unidades de infantería ligero protegida.<br /

Main Reproductive Indicators and Environmental Factors that Affect Siboney and Mambi de Cuba Cows at a Breeding Company in Central Cuba

Background: The association of trait heritability with milk production, breeding, and longevity, was thoroughly studied in the past decade. However, the efficiency of productive and reproductive performance is determined by the action of environmental factors and inappropriate husbandry. Therefore, the main reproductive indicators and environmental factors affecting cow genotypes Cuban Siboney and Cuban Mambí were evaluated at a genetic breeding company in central Cuba. Methods: The individual records of 618 females were processed between 2007 and 2010 (358 Mambí de Cuba from six different herds, and 260 Siboney de Cuba from four farms). The calving-first insemination service (CFIS) intervals, the calving-gestation (CG) interval, and the calving interval (CI) were determined. The effects of various factors on the reproductive indicators were estimated using a general linear model. Results: The farm factor had a significant influence (P&nbsp;&lt;&nbsp;0.05) on CFIS, CG, and CI in both genotypes. Calving years had a significant effect (P&nbsp;&lt;&nbsp;0.05) on CFIS, CG, and CI, with the best results in 2009 and 2010. The best calving quarter for reproductive indicators was the July-August-September period, with a significant influence (P&nbsp;&lt;&nbsp;0.05) on CFIS, CG, and CI, in Mambi de Cuba, whereas Siboney de Cuba influenced the CFIS. Conclusions: The two genotypes showed a remarkable deterioration of the reproductive indicators evaluated, particularly influenced by farm, calving year, and calving quarter.&nbsp; Background: The association of trait heritability with milk production, breeding, and longevity, was thoroughly studied in the past decade. However, the efficiency of productive and reproductive performance is determined by the action of environmental factors and inappropriate husbandry. Therefore, the main reproductive indicators and environmental factors affecting cow genotypes Cuban Siboney and Cuban Mambí were evaluated at a genetic breeding company in central Cuba. Methods: The individual records of 618 females were processed between 2007 and 2010 (358 Mambí de Cuba from six different herds, and 260 Siboney de Cuba from four farms). The calving-first insemination service (CFIS) intervals, the calving-gestation (CG) interval, and the calving interval (CI) were determined. The effects of various factors on the reproductive indicators were estimated using a general linear model. Results: The farm factor had a significant influence (P&nbsp;&lt;&nbsp;0.05) on CFIS, CG, and CI in both genotypes. Calving years had a significant effect (P&nbsp;&lt;&nbsp;0.05) on CFIS, CG, and CI, with the best results in 2009 and 2010. The best calving quarter for reproductive indicators was the July-August-September period, with a significant influence (P&nbsp;&lt;&nbsp;0.05) on CFIS, CG, and CI, in Mambi de Cuba, whereas Siboney de Cuba influenced the CFIS. Conclusions: The two genotypes showed a remarkable deterioration of the reproductive indicators evaluated, particularly influenced by farm, calving year, and calving quarter

Nuevo banco de ítems para evaluar adaptativamente los Cinco Grandes

Even though the Five Factor Model (FFM) has been the dominant paradigm in personality research for the past two decades, very few studies have measured the FFM adaptively. Thus, the purpose of this research was the building of a new item pool to develop a computerized adaptive test (CAT) for personality assessment. Method: A pool of 480 items that measured the FFM facets was developed and applied to 826 participants. Facets were calibrated separately and item selection was performed being mindful of the preservation of unidimensionality of each facet. Then, a post-hoc simulation study was carried out to test the performance of separate CATs to measure the facets. Results: The final item pool was composed of 360 items with good psychometric properties. Findings reveal that a CAT administration of four items per facet (total length of 120 items) provides accurate facets scores, while maintaining the factor structure of the FFM. Conclusions: An item pool with good psychometric properties was obtained and a CAT simulation study demonstrated that the FFM facets could be measured with precision using a third of the items in the poolA pesar de que el Modelo de los Cinco Factores (MCF) ha sido el paradigma predominante durante las últimas dos décadas, muy pocos estudios han medido el MCF de forma adaptativa. El objetivo de esta investigación fue construir un nuevo banco de ítems para desarrollar un test adaptativo informatizado (TAI) para evaluar la personalidad. Método: se desarrolló un banco de 480 ítems para evaluar las facetas del MCF y se aplicó a 826 participantes. Cada faceta se calibró por separado y la selección de ítems se realizó atendiendo a que cada faceta fuese unidimensional. Después se realizó un estudio de simulación post-hoc para evaluar la efi ciencia de TAIs a nivel de facetas. Resultados: el banco final estaba formado por 360 ítems con buenas propiedades psicométricas. Los resultados demostraron que la aplicación adaptativa de cuatro ítems por faceta proporciona puntuaciones precisas en las mismas, al mismo tiempo que se mantiene la estructura factorial del MCF. Conclusiones: el banco final está formado por ítems con buenas propiedades psicométricas. La aplicación adaptativa del banco permite medir la personalidad de forma eficiente a nivel de facetas utilizando una tercera parte de los ítemsThe research has been funded by the Ministry of Economy and Competitivity of Spain (PSI2013-44300-P), and the UAM-IIC Chair «Psychometric Models and Applications

Careón ophiolite, NW Spain: Suprasubduction zone setting for the youngest Rheic Ocean fl oor

The Careón ophiolite (Galicia, NW Iberian Massif) shows lithological and geochemical features suggestive of an origin in a suprasubduction zone setting. As with other Devonian ophiolites in the European Variscan belt, it was generated within a contracting Rheic Ocean. This setting and the general absence of large Silurian-Devonian volcanic arcs on both of the Rheic Ocean margins strongly suggest that this ocean was closed by intraoceanic subduction directed to the north. This subduction removed the older normal (N) mid-oceanic-ridge basalt (MORB) oceanic lithosphere and gave rise to a limited volume of new suprasubduction zone oceanic lithosphere. The Careón ophiolite is a key element in understanding the evolution of the Rheic Ocean, which was the main oceanic domain that closed during the Paleozoic convergence of Gondwana and Laurussia, preceding the assembly of Pange