ABSTRACT
The purpose of this paper was to introduce the theoretical basis of the causal mediation effect analysis and the specific method to realize an example by the causal mediation effect analysis with SAS. The theoretical basis of the causal mediation effect analysis included the following two aspects， the basic concept and defining the counterfactual framework of the causal mediation effect. The example was about whether the encouraging environment provided by parents would affect the cognitive development of children. The traditional multiple linear regression analysis， the causal mediation effect analysis without considering covariates and with considering covariates were used， respectively. By comparing the results obtained by the three analysis methods， the following conclusions were drawn： ① when there were the mediation variables in the data， it was not suitable to use traditional multiple linear regression analysis to replace the causal mediation effect analysis； ② when there were covariates in the data， it was not suitable to conduct causal mediation analysis under the condition of ignoring covariates.
ABSTRACT
La planeación adecuada de una investigación en ciencias de la salud es necesaria para determinar la información que debe ser recolectada y que permitirá lograr los objetivos del estudio. Esta información conforma el grupo de variables que permiten, a su vez, realizar una aproximación a priori a la metodología de análisis de los datos. Este artículo académico busca aclarar la terminología empleada al hablar de variables y mostrar una forma sencilla de su presentación en un protocolo o proyecto de investigación. [Castro-Jiménez MA, Díaz-Martínez LA. Las variables en el proceso de investigación en salud: importancia, clasificación y forma de presentación en protocolos de investigación. MedUNAB 2009; 12:151-156]
A careful planning of any epidemiological of clinical research, including thesis in any area of the health sciences, is necessary to determine what information should be gathered in order to achieve the study's objectives. This information defines the set of variables that, in turn, make an a priori approach to the metodology of data analysis. This academic paper is aimed to clarify the terminology used when talking about variables and show a simple way to describe them on a research project or protocol. [Castro-Jiménez MA, Díaz-Martínez LA. Variables in health research process: importance, classification, and show way in research protocols. MedUNAB 2009; 12:151-156].