Confiabilidad de una escala de valoración de resúmenes para congresos

Introducción: En 2013, desarrollamos una escala, para evaluar resúmenes de congresos de la Sociedad de Cirujanos de Chile (SOCICH). Objetivo: Determinar consistencia interna y confiabilidad interobservador de una escala para evaluar resúmenes de congresos. Material y Método: Estudio de confiabilidad. Doce cirujanos fueron capacitados de forma virtual durante 8 horas, para aplicar la escala. Una vez finalizado el entrenamiento, se les envió un cuestionario para evaluar contenidos de la capacitación, y varios resúmenescasos para ser evaluados con la escala antes señalada. Se aplicó estadística descriptiva, luego se estimó el grado de acuerdo entre observadores para cada ítem de la escala. Posteriormente, se evaluó el coeficiente de correlación (CCI), utilizando un modelo de dos factores mixtos en el que los efectos de los evaluadores son aleatorios y los ítems fijos; utilizando una definición de acuerdo absoluto. Además, se evaluó la consistencia interna de los ítems utilizando alfa de Cronbach, considerando intérvalos de confianza del 95% (IC 95%). Resultados: Luego de analizar las mediciones de los 9 ítems por los 12 observadores, se verificó que el CCI fue de 0,871; con un IC 95% de 0,700; 0,965. El valor de la consistencia interna fue de 0,7 considerando los 9 ítems, no se recomienda eliminar ningún ítem. Conclusión: La escala tiene buena confiabilidad interobservador y los ítems son consistentes entre sí; por lo que puede ser considerada como un instrumento confiable para la valoración de resúmenes de congresos.

Background: In 2013, we developed a scale to evaluate the abstracts of the congresses of the Society of Surgeons of Chile (SOCICH). Objective: To determine internal consistency and interobserver reliability of a scale to evaluate conference abstracts. Material and Methods: Reliability study. Twelve surgeons were trained virtually for 8 hours, to apply the scale. Once the training was finished, they were sent a questionnaire to evaluate the contents of the training, and several summaries-cases to be evaluated with the aforementioned scale. Descriptive statistics were applied, then the degree of agreement between observers was estimated for each item of the scale. Subsequently, intraclass correlation coefficient (ICC) was evaluated, using a mixed two-factor model where the effects of the evaluators are random and the items are fixed, using a definition of absolute agreement. In addition, the internal consistency of the items was evaluated using Cronbach's alpha, considering 95% confidence intervals (95% CI). Results: After analyzing the measurements of the 9 items by the 12 observers, it was verified that the ICC was 0.871; with a 95% CI of 0.700; 0.965. The internal consistency value was 0.7 considering the 9 items, it is not recommended to delete any item. Conclusions: The scale has good internal consistency and interobserver reliability. Therefore, it can be considered as reliable instrument to be used in the evaluation of abstracts for congresses.

An R Function for Cronbach’s Alpha Analysis: A Case-Based Approach

Cronbach’s alpha is a very commonly used method in biomedical research. Cronbach’s alpha Indicates the extent to which the items in your questionnaire are related to each other, a useful coefficient for assessing the internal consistency of the items. Although this method is commonly used in medical research, the statistical software packages do not have the direct menu-driven operation for Cronbach’s alpha. Hence this paper intends to provide an R function (Cronbach. Alpha) for Cronbach’s alpha analysis.

Development of age appropriate vision function questionnaire for children with visual impairment (CHVI-VFQ)

Purpose: To develop a new age?appropriate visual function questionnaire for visually impaired children. Methods: The study was conducted in north India in 20,955 (97.3%) children ?15 years who underwent visual acuity examination. Of these 20,955 children, a total of 722 children were referred with unaided visual acuity less than 6/12 in any eye. Among these referred children, parents in the age group of 5–9 years and children between 10 and 15 years underwent interviews using LV Prasad Functional Visual Questionnaire?20 (LVP FVQ 20) and Indian Visual Functioning Questionnaire?33 (IND VFQ?33). Following this, multiple steps were undertaken that involved expert opinion for the removal of items on basis of zero variance and factor analysis along with calculation of Cronbach’s alpha. Results: A Cronbach’ alpha of 0.834 was calculated for the younger age group and 0.931 for the higher age group of children. Conclusion: A new robust age?appropriate questionnaire was developed and it was observed that there was a significant change in median score (that was derived for various domains after calculating the median for the items in various domains asked pre? and post?intervention in the form of glasses or surgery) for quality of visual function in the visually impaired children. A significant change in functional vision of visually impaired children (P < 0.005) was observed in both age groups

Preparation and validation of a new questionnaire to study faculty perception of online teaching - Use of Cronbach’s alpha and pilot.

Background: The COVID-19 pandemic has forced educators to shift to virtual online classes. Teachers being major stakeholders in the medical teaching-learning process, it becomes important to understand their perception towards this new endeavour. It will make this transition beneficial to the learners. Objectives: To document the process of validation of a new questionnaire devised to study the perception of medical undergraduate teaching faculty towards online classes, using Cronbach’s alpha, and the subsequent pilot for the same. Results: At initial validation, Cronbach’s alpha was not acceptable (0.65) for the questionnaire. One item was scored low by two validators and was removed. Three items were given poor rating for lay out, clarity and feasibility and required editing. The Cronbach’s alpha after revision was 0.92 (acceptable). Pilot study was conducted. Based on the proportion of positive perception (36.4%) regarding ongoing online teaching programme, conducted on 11 teaching faculty with 10% absolute precision and 95% confidence, the minimum sample size for the main study was calculated to be 89. This was feasible from the point of view of total faculty strength. Conclusion: Research work involving a new tool, such as questionnaire, must utilize the statistical tool Cronbach’s alpha for validation, and pilot study for estimating the sample size and testing the content validity.

Evaluación psicométrica de la escala de depresión de Yesavage en adultos mayores latinoamericanos: Estudios SABE y CRELES / Psychometric evaluation of the abbreviated scale of Yesavage depression in older adults in several cities in Latin America: Studies SABE and CRELES

Resumen Con el cambio en los patrones demográficos y las mejoras en los sistemas de salud, se espera un aumento de la población adulta mayor en el mundo y especialmente en América Latina. Esto genera un aumento en la prevalencia de enfermedades crónicas y degenerativas; una de ellas es la depresión. La depresión supone costos sociales y financieros que pueden causar trastornos a la salud y a la vida cotidiana de quien la padece y de quienes están alrededor, ya que conduce a una morbilidad y mortalidad altas. El presente estudio pretende proporcionar más evidencia psicométrica sobre la idoneidad dela Escala corta de Yessavage (GDS-15) como instrumento para identificar síntomas depresivos en varias poblaciones de adultos mayores, sin patologías específicas, de diferentes países de Latinoamérica. Se utilizaron los datos de los estudios de la Encuesta sobre Salud, Bienestar y Envejecimiento en América Latina y el Caribe (SABE) y Costa Rica, y el Estudio de Longevidad y Envejecimiento Saludable (CRELES). Se hizo uso de la teoría clásica de los tests y un modelo de Rasch. Se encontró que la escala presenta buenos indicadores de consistencia interna con Alphas de Cronbach superiores a .8 en la mayoría de los países. Cuando se evalúa con el modelo de Rasch se identifican varios ítems que no ajustan al modelo, lo que podría relacionarse con los contextos culturales o al hecho de ser población general, por lo que se sugiere que se evalúe el efecto de factores sociales, demográficos, culturales, educativos, roles de género y red de apoyo social en un modelo multinivel.

Abstract Changes in demographic patterns, as well as improvements in health systems, increase the elderly population in the world and especially in Latin America. These processes increase the prevalence of chronic and degenerative diseases such as depression. Depression involves social and financial costs that can cause disorders to the health and daily life of those who suffer from it and those around them, such as high morbidity and mortality. This study uses classical test theory and Rasch model to seek for psychometric evidence to support the suitability of Yesavage's short-scale questionnaire (GDS-15) as a suitable instrument to identify depressive symptoms in general older adult populations in Latin America. The unidimensionality of the scale in each country was validated by performing a factorial analysis of principal components with a tetrachoric correlation matrix. Cronbach's Alpha was also calculated as an indicator of the internal validity of the scale and in order to provide the values of this indicator and compare it with other studies. Using a Rasch model, this study evaluated whether there are items that present difficulties in being answered or, conversely, that do not contribute to the measurement of depression. The Rasch analysis is based on a mathematical model that describes the relationship between the probability of a correct response to an item and the difference between the ability of the respondent. This model allows the joint measurement of people and items in the same construct. By doing this, a person's interpretation of scores is richer than just ranking from percentiles. The Survey on Health, Well-Being, and Aging in Latin America and the Caribbean (Project SABE) was used, a cross-sectional study that examines health conditions and functional limitations of persons aged 60 and older in the countries of Argentina, Barbados, Brazil, Chile, Cuba, Mexico, and Uruguay. This study also used the Costa Rican Longevity and Healthy Aging Study (CRELES), a set of nationally representative longitudinal surveys of health and life course experiences of older Costa Ricans. The scale shows good internal consistency. Cronbach's Alpha was 0.8 and more in most countries. Nevertheless, the Rasch model identified some items that do not fit the model. These items are: "Have you dropped or doing less of many of your activities and interests?", "Were you afraid that something bad was going to happened to you?", "Did you prefer to stay at home instead of going out and doing new things?", "Did you feel you have more problems with your memory that other people your age?", "Did you feel full of energy?", "Did you think that most people were better off than you?". It is important to mention that these items also present drafting problems. In the case of the item "Did you prefer to stay at home instead of going out and doing things?", it can be thought that in the case of some Latin American countries, the preference for staying at home could be more related to the social and political context in which you live with depression. On the other hand, these results also invite us to think about the existence of various dimensions on this scale. Lack of fit is related to cultural contexts or to the fact that the data refers to a general population. Social, demographic, cultural, educational factors, gender roles, and social support networks could be evaluated in a multilevel model.

Application of the Chinese version of the Addenbrooke＇s cognitive examination－Ⅲ in presbycusis with mild cognitive impairment / 中国基层医药

Objective To explore the reliability , validity and best cut －off value of Chinese version Addenbrooke＇s cognitive examination －Ⅲ(ACE－Ⅲ) in presbycusis patients with mild cognitive impairment (MCI). Methods A total of 43 presbycusis patients with mild cognitive impairment ,61 presbycusis patients with normal cognitive impairment and 60 healthy controls treated in outpatient clinic of department of otolaryngology in the Affiliated Hospital of Yangzhou University from January 2016 to October 2017 were enrolled.The Chinese version of mini mental state examination(MMSE),Montreal cognitive assessment ( MoCA) and ACE －Ⅲ were used to evaluate cognitive function of subjects.The reliability and validity of the ACE －Ⅲwere analyzed with the SPSS 21.0,and the cut－off point was confirmed with the receiver operating characteristic ( ROC) curve analysis, and the value of the scale questionnaire in the diagnosis of presbycusis patients with MCI was assessed.Results Chinese version of ACE －Ⅲhad betler feasiblity, and the receiving rate, recovery rate and effivience were 100.0%, 100.0% and 94.9%, respetively.The Cronbach＇s alpha,split－half reliability and intraclass correlation coefficient were 0.870(P＜0.05), 0.874(P＜0.05) and 0.880(P＜0.05),respectively.The patients in MCI group got a lower score in the sub －scale of attention／orientation,memory,verbal fluency,language and visual space of ACE －Ⅲ compared with those in NCI group and healthy control group ,and the differences were statistically significant ( F ＝48.042,46.594,35.442, 19.374,256.19,140.319,all P＜0.001).The criteria validity calculated between the Chinese version of ACE －Ⅲand MMSE was 0.802 (P＜0.001).Factor analysis of the construct validity showed that the 26 items were classed into five domains.Every domain was sensitive and effective to discriminate between patients and healthy individuals (P＜0.05).The Chinese version of ACE －Ⅲ showed significantly correlation with the total scores of MoCA ( r＝0.802,P＜0,001).When the cut －off value for diagnosis was 86.5,the largest area under the ROC curve for the Chinese version of ACE－Ⅲwas 0.98(95%CI:0.897－0.996).The relative sensitivity and specificity were 100.0%and 95.0%,respectively.Conclusion The Chinese version of ACE －Ⅲ had better internal consistency ,reliability and validity,and is applicable for MCI assessment in elderly patients with presbycusis.Patients with presbycusis can be considered to have cognitive dysfunction with score of 86.5 by using this questionnaire.

Application of the Chinese version of the Addenbrooke's cognitive examination-Ⅲ in presbycusis with mild cognitive impairment / 中国基层医药

Objective@#To explore the reliability, validity and best cut-off value of Chinese version Addenbrooke's cognitive examination-Ⅲ(ACE-Ⅲ) in presbycusis patients with mild cognitive impairment(MCI).@*Methods@#A total of 43 presbycusis patients with mild cognitive impairment, 61 presbycusis patients with normal cognitive impairment and 60 healthy controls treated in outpatient clinic of department of otolaryngology in the Affiliated Hospital of Yangzhou University from January 2016 to October 2017 were enrolled.The Chinese version of mini mental state examination(MMSE), Montreal cognitive assessment(MoCA) and ACE-Ⅲ were used to evaluate cognitive function of subjects.The reliability and validity of the ACE-Ⅲ were analyzed with the SPSS 21.0, and the cut-off point was confirmed with the receiver operating characteristic(ROC) curve analysis, and the value of the scale questionnaire in the diagnosis of presbycusis patients with MCI was assessed.@*Results@#Chinese version of ACE-Ⅲ had betler feasiblity, and the receiving rate, recovery rate and effivience were 100.0%, 100.0% and 94.9%, respetively.The Cronbach's alpha, split-half reliability and intraclass correlation coefficient were 0.870(P<0.05), 0.874(P<0.05) and 0.880(P<0.05), respectively.The patients in MCI group got a lower score in the sub-scale of attention/orientation, memory, verbal fluency, language and visual space of ACE-Ⅲ compared with those in NCI group and healthy control group, and the differences were statistically significant (F=48.042, 46.594, 35.442, 19.374, 256.19, 140.319, all P<0.001). The criteria validity calculated between the Chinese version of ACE-Ⅲ and MMSE was 0.802 (P<0.001). Factor analysis of the construct validity showed that the 26 items were classed into five domains.Every domain was sensitive and effective to discriminate between patients and healthy individuals(P<0.05). The Chinese version of ACE-Ⅲ showed significantly correlation with the total scores of MoCA(r=0.802, P<0, 001). When the cut-off value for diagnosis was 86.5, the largest area under the ROC curve for the Chinese version of ACE-Ⅲ was 0.98(95% CI: 0.897-0.996). The relative sensitivity and specificity were 100.0% and 95.0%, respectively.@*Conclusion@#The Chinese version of ACE-Ⅲ had better internal consistency, reliability and validity, and is applicable for MCI assessment in elderly patients with presbycusis.Patients with presbycusis can be considered to have cognitive dysfunction with score of 86.5 by using this questionnaire.

Análisis factorial exploratorio como método multivariante para validación de datos académicos en plataformas virtuales / Exploratory factorial analysis as a multivariate method for the validation of academic data in virtual platforms / Análise fatorial exploratória como método multivariado para a validação de dados acadêmicos em plataformas virtuais

Resumen Introducción: El trabajo se establece como un resultado de investigación en el cual se realiza una revisión bibliográfica sobre la temática planteada. Objetivo: Caracterizar los materiales de clase que utiliza dos universidades una pública y una privad para la identificación de tipos de tecnologías. Materiales y Método: Se considera que el estudio es no-experimental y se espera la participaron todos los estudiantes matriculados en el primer semestre 2017, se cumple con los criterios de inclusión: a) edad mínima de 18 años; b) matriculados en sus respectivas universidades; La muestra aleatoria piloto contenía 98 participantes de un total de 2150 estudiantes de las dos universidades. Resultados: Mediante la aplicación de varias técnicas estadísticas como el análisis: Factorial Exploratorio, alfa de Cronbach clásico. Se analizó el comportamiento de las respuestas al cuestionario de 21 ítems, que tiene un formato de escala tipo Likert, definidas en 4 dimensiones. Se comprobó la inexistencia de diferencias estadísticamente significativas, en tres ítems del estudio. Conclusiones: Se ha analizado la validez y fiabilidad de dicho cuestionario a través de un análisis factorial de componentes principales con rotación Varimax. Se concluye que bastaría con introducir adaptaciones en la relación de dimensiones propuestas en este cuestionario que tuviera en cuenta las especificidades de cada material de estudio.

Abstract Introduction: The work is established as a result of research in which a bibliographic review is made on the subject matter proposed. Objective: Characterize the class materials used by two universities, one public and one private for the identification of types of technologies. Materials and Method: The study is considered non-experimental and it is expected that all students enrolled in the first semester of 2017 will participate, complying with the inclusion criteria: a) minimum age of 18; b) enrolled in their respective universities; The pilot random sample contained 98 participants out of a total of 2150 students from the two universities. Results: Through the application of several statistical techniques such as the analysis: Exploratory Factorial, classic Cronbach's alpha. The behavior of the responses to the 21-item questionnaire, which has a Likert-type scale format, was analyzed, defined in 4 dimensions. The absence of statistically significant differences was verified in three items of the study. Conclusions: The validity and reliability of this questionnaire was analyzed through a factorial analysis of principal components with Varimax rotation. It is concluded that it would be enough to introduce adaptations in the list of dimensions proposed in this questionnaire that took into account the specificities of each study material.

Resumo Introdução: O trabalho é estabelecido como resultado de uma pesquisa em que é feita uma revisão bibliográfica sobre o assunto proposto. Objetivo: caracterizando os materiais de aula utilizados por duas universidades, uma pública e outra privada para a identificação de tipos de tecnologias. Materiais e Método: O estudo é considerado não experimental e espera-se que todos os alunos matriculados no primeiro semestre de 2017 participem, obedecendo aos critérios de inclusão: a) idade mínima de 18 anos; b) matriculados em suas respectivas universidades; A amostra aleatória piloto continha 98 participantes de um total de 2150 estudantes das duas universidades. Resultados: Através da aplicação de diversas técnicas estatísticas, como a análise: Fatorial Exploratório, clássico Alfa de Cronbach. Analisou-se o comportamento das respostas ao questionário de 21 itens, que possui formato de escala tipo Likert, definido em 4 dimensões. A ausência de diferenças estatisticamente significantes foi verificada em três itens do estudo. Conclusão: A validade e confiabilidade deste questionário foram analisadas através de uma análise fatorial de componentes principais com rotação Varimax. Conclui-se que seria suficiente introduzir adaptações na lista de dimensões proposta neste questionário que levasse em consideração as especificidades de cada material de estudo.

Validation of the Malay version of the Amsterdam Preoperative Anxiety and Information Scale (APAIS)

Background: Preoperative anxiety is a significant problem worldwide that may affect patients’ surgical outcome. By using a simple and reliable tool such as the Amsterdam Preoperative Anxiety and Information Scale (APAIS), anaesthesiologists would be able to assess preoperative anxiety adequately and accurately. Objective: The purpose of this study was to develop and validate the Malay version of APAIS (Malay-APAIS), and assess the factors associated with higher anxiety scores. Methods: The authors performed forward and backward translation of APAIS into Malay and then tested on 200 patients in the anaesthetic clinic of University Malaya Medical Centre. Psychometric analysis was performed with factor analysis, internal consistency and correlation with Spielberger’s State-Trait Anxiety Inventory (STAI-state). Results: A good correlation was shown with STAI-state (r = 0.59). Anxiety and need for information both emerged with high internal consistency (Cronbach’s alpha 0.93 and 0.90 respectively). Female gender, surgery with a higher risk and need for information were found to be associated with higher anxiety scores. On the other hand, previous experience with surgery had lower need for information. Conclusion: The Malay-APAIS is a valid and reliable tool for the assessment of patients’ preoperative anxiety and their need for information. By understanding and measuring patient’s concerns objectively, the perioperative management will improve to a much higher standard of care.

Usos del coeficiente alfa de Cronbach en el análisis de instrumentos escritos / The usage of the Cronbach Coefficient alpha in the Analysis of the Written Instruments

Se realizó un estudio de carácter evaluativo para determinar la precisión de un examen escrito mediante un análisis de fiabilidad. El examen, integrado por 30 preguntas que exploran cierto tipo de conocimiento profesional, se aplicó a 45 personas, y con los puntajes obtenidos se creó una base de datos en SPSS para Windows, versión 16. Se calculó el coeficiente alfa de Cronbach, para diferentes partes del examen y coeficientes de discriminación para determinar las variables más relevantes a los efectos de la confiabilidad del examen. Los resultados principales se presentaron en tablas. Se obtuvo un valor negativo para la confiabilidad del examen, y mediante eliminación de preguntas y cambio de escala de los puntajes, se obtuvo un examen de confiabilidad aceptable. Se concluyó que el análisis de fiabilidad es un procedimiento efectivo para incrementar la precisión de un examen

It was performed a study, to evaluate the precision of a written test by means of a reliability analysis. The test, with 30 questions exploring some kind of professional knowledge, was applied to a set of 45 persons. Using the SPSS for Windows Version 16 software, a data base was created with the scores obtained. We calculated the Cronbach alpha coefficients for different parts of the test and the corresponding indexes of discrimination in order to determine the most relevant variables related with the reliability of the test. The principal findings were presented in statistical tables. A negative value of the reliability coefficient was obtained for the initial test, but, by means of putting out some questions and making appropriate changes in the score scales of them, a new version of the test with a medium level of reliability was obtained. It was concluded that the reliability analysis is an effective tool to increase the precision of a test

Evaluation of Reliability and Validity of the Louisville Instrument for Transplantation(LIFT) in Korean Population

PURPOSE: Composite tissue allotransplantation has emerged as a new therapeutic modality to reconstruct major tissue defects of the head, neck and extremities. A questionnaire-based instrument, the Louisville Instrument for Transplantation(LIFT), has been developed to objectively assess the risk-versus-benefit ratio for composite tissue allotransplantation procedures. The objective of this study is to assess if the LIFT is a useful, reliable and valid tool to apply to the Korean population. METHODS: Seventy-three medical students and 60 lay public completed the LIFT questionnaire(translated to Korean) over the period from February 2010 to April 2010. Internal consistency was assessed using Cronbach's alpha. Test-retest reliability was analyzed using Pearson's correlation coefficient. Construct validity was assessed by comparing Pearson's correlation coefficients between perceived improvements in quality of life and responses to risk tolerance questions concerning organ transplants. RESULTS: Measurements of the test-retest reliability showed that Pearson's correlation coefficients ranged from 0.241 to 0.902, and Cronbach's alphas ranged from 0.52 to 0.80 for medical students and from 0.63 to 0.83 for the lay public. Pearson's correlation coefficients showed significant correlations between perceived improvements in quality of life and responses to risk tolerance questions concerning organ transplants. Hand transplant showed a significant correlation in medical students. Foot, hand, two hands, larynx, partial face transplants showed significant correlations for the lay public. CONCLUSION: The applicability of the LIFT to the Korean population was found to be reliable and valid. The LIFT may serve as a useful tool for clinical application in the Korean population.

Coeficientes de confiabilidad de instrumentos escritos en el marco de la teoría clásica de los tests / Reliability coefficient of written tools in the frame of the classical theory of tests

Evaluar la confiabilidad en el marco de la teoría clásica de los tests y precisar las condiciones bajo las cuales el coeficiente alfa de Cronbach constituye la mejor alternativa. El coeficiente alfa de Cronbach es el recurso numérico más utilizado para evaluar la confiabilidad de instrumentos escritos. Como prueba de esto, baste decir que desde su publicación en 1951 hasta la fecha, ha sido citado más de 5 590 veces. Sin embargo, se ha comprobado que en no pocas situaciones este coeficiente no es la mejor alternativa para evaluar la confiabilidad. Se discutieron varias alternativas para la evaluación de la confiabilidad y se precisaron las condiciones bajo las cuales el coeficiente alfa de Cronbach constituye la mejor alternativa. La teoría clásica de los tests constituye un modelo apropiado para desarrollar el concepto de confiabilidad y las diferentes fórmulas de cálculo de mayor utilidad en las aplicaciones, el coeficiente alfa de Cronbach es el indicador más utilizado para cuantificar la consistencia interna de los tests y es necesario tener en cuenta los supuestos que sustentan la correcta aplicación del coeficiente alfa para hacer una interpretación adecuada de su valor numérico.

To assess reliability in the frame of the classical theory of tests and to exactly specify the conditions under which Cronbach's alpha coefficient is the best option. Cronbach's alpha coefficient is the most used numerical resort to evaluate the reliability of written tools. As a proof, it is enough to say that from its publication in 1951 up to now, it has been cited more than 5 590 times. However, it has been proved that this coefficient is not always the best option to assess reliability. Various alternatives were discussed for the assessment of reliability, and the conditions under which Cronbach's alfa coefficient is the best choice were determined. The classical theory of tests is an appropriate model to develop the concept of reliability and the calculation formulae more useful for the applications. This coefficient is the most used indicator to quantify the internal consistency of tests, and it is necessary to bear in mind the suppositions that support the correct application of alpha coefficient to make a proper interpretation of its numerical value.

Aproximación al uso del coeficiente alfade Cronbach / An Approach to the Use of Cronbach’s Alfa

Introducción: Las escalas se usan frecuentemente en la investigación y en la práctica clínica de la psiquiatría. No obstante, todas las escalas deben ser formalmente validadas antes, con el propósito de conocer de las propiedades psicométricas en una población específica. Descripción: Las escalas pueden ser validadas con el uso de un patrón de referencia o sin él; la segunda opción es la única forma de validar algunos instrumentos. Establecer la consistencia interna de una escala es una aproximación a la validación del constructo y consiste en la cuantificación de la correlación que existe entre los ítems que la componen. Valores de alfa de Cronbach entre 0,70 y 0,90 indican una buena consistencia interna. La determinación del alfa de Cronbach se indica para escalas unidimensionales entre tres y veinte ítems. Se debe informar este valor cada vez que se emplee la escala y puede usarse como única medida de validez cuando es difícil una validación con un patrón de referencia.

Introduction: Scales are frequently used in clinical and research psychiatry. However, scales must be validated in order to know their psychometric properties when they are administered to special populations. Description: Establishing the internal consistency of a scale is an approach to validate its construct. That is, the quantification of the correlation among the items includes in a scale. Cronbach’ alpha values between 0.70 and 0.90 suggest a good internal consistency. The Cronbach’ alpha coefficient may be estimated when a three- to twenty-item one-dimensional scale is administered and particularly when it is difficult to conduct a validation study against a gold standard.

Reliability of the Dynamic Stereoacuity using New Personal Computer Program

PURPOSE: We performed this study to evaluate the reliability of dynamic stereoacuity test with new personal computer program. METHODS: Twenty subjects (5 men, 15 women) were examined for dynamic stereo-threshold measured by new computer program at 94cm test distance. On fifty tested subjects, variant dynamic stereoacuity was created with the random spherical lenses from +0.5 to +3.0 diopter before the right eye. To evaluate the intraobserver reliability of the test, stereoacuity was measured five times on five separate days by the same examiner. To evaluate the interobserver reproducibility, stereoacuity was measured two times by two different examiners. RESULT: The Cronbach's alpha (internal consistency) of intraobserver was 0.99 (P<0.001). The Spearman correlation coefficient of interobserver was 0.99 (P<0.001). CONCLUSION: This method of dynamic stereoacuity measurement has a high reliability.