A classification system for research designs in psychology. Abstract: This work presents a conceptual framework and develops basic principles to promote a classification system for the most common research designs in psychology based on three strategies (manipulative, associative and descriptive) from which different types of studies emerge, three for the manipulative strategy (experimental, quasi-experimental and single-case), three for the associative strategy (comparative, predictive and explanatory) and two for the descriptive strategy (observational and selective). Keywords: Research methodology; research design; experimental design; non-experimental design. The paper discusses the importance of having a conceptual framework for researchers to situate their research projects, understand the basic principles underlying methodological review, and have a repertoire of designs to plan their research appropriately. The main objective is to present a conceptual framework for evaluating the research process and a proposal for classifying the most commonly used empirical research designs in basic and applied psychology. The paper outlines the three pillars of the research process: design, measurement, and analysis, which are closely related to the four forms of validity in research proposed by Campbell and colleagues (Shadish, Cook & Campbell, 2002): internal validity, statistical conclusion validity, construct validity, and external validity. The design is defined as a plan that provides a structure for integrating all elements of an empirical study to ensure that results are credible, unbiased, and generalizable. The measurement involves identifying, defining, and measuring observable and non-observable variables, and generating numerical or empirical data that is input into statistical analysis procedures. The analysis involves estimating parameters and testing hypotheses about the research objective using appropriate statistical procedures. The paper also discusses the basic principles in the design and evaluation of research. These include: 1) Every research is designed to answer a specific objective. 2) The most important reason for publishing a research article is to enable its replication to develop a coherent scientific knowledge. 3) In terms of measuring the variables of the research, an article must include detailed information about the instruments used to collect data and the nature of the empirical data, including the definition and operationalization of the variables. 4) In terms of statistical analysis, the statistical methods used must be described in sufficient detail to be understood by other researchers, as well as the procedures for handling missing data. 5) In terms of design, the research report must include a detailed description of the participants, the experimental conditions (if a treatment or program is introduced) or the context in which the study is conducted (if no treatment is present), and the procedures for controlling extraneous variables (internal validity) as well as an evaluation of the generalizability of the findings (external validity). The paper also discusses the importance of having a classification system for research designs in psychology. It proposes a classification system based on three strategies: manipulative, associative, and descriptive. The manipulative strategy includes three types of studies: experimental, quasi-experimental, and single-case.A classification system for research designs in psychology. Abstract: This work presents a conceptual framework and develops basic principles to promote a classification system for the most common research designs in psychology based on three strategies (manipulative, associative and descriptive) from which different types of studies emerge, three for the manipulative strategy (experimental, quasi-experimental and single-case), three for the associative strategy (comparative, predictive and explanatory) and two for the descriptive strategy (observational and selective). Keywords: Research methodology; research design; experimental design; non-experimental design. The paper discusses the importance of having a conceptual framework for researchers to situate their research projects, understand the basic principles underlying methodological review, and have a repertoire of designs to plan their research appropriately. The main objective is to present a conceptual framework for evaluating the research process and a proposal for classifying the most commonly used empirical research designs in basic and applied psychology. The paper outlines the three pillars of the research process: design, measurement, and analysis, which are closely related to the four forms of validity in research proposed by Campbell and colleagues (Shadish, Cook & Campbell, 2002): internal validity, statistical conclusion validity, construct validity, and external validity. The design is defined as a plan that provides a structure for integrating all elements of an empirical study to ensure that results are credible, unbiased, and generalizable. The measurement involves identifying, defining, and measuring observable and non-observable variables, and generating numerical or empirical data that is input into statistical analysis procedures. The analysis involves estimating parameters and testing hypotheses about the research objective using appropriate statistical procedures. The paper also discusses the basic principles in the design and evaluation of research. These include: 1) Every research is designed to answer a specific objective. 2) The most important reason for publishing a research article is to enable its replication to develop a coherent scientific knowledge. 3) In terms of measuring the variables of the research, an article must include detailed information about the instruments used to collect data and the nature of the empirical data, including the definition and operationalization of the variables. 4) In terms of statistical analysis, the statistical methods used must be described in sufficient detail to be understood by other researchers, as well as the procedures for handling missing data. 5) In terms of design, the research report must include a detailed description of the participants, the experimental conditions (if a treatment or program is introduced) or the context in which the study is conducted (if no treatment is present), and the procedures for controlling extraneous variables (internal validity) as well as an evaluation of the generalizability of the findings (external validity). The paper also discusses the importance of having a classification system for research designs in psychology. It proposes a classification system based on three strategies: manipulative, associative, and descriptive. The manipulative strategy includes three types of studies: experimental, quasi-experimental, and single-case.