Research Methods Map
Explore the methods map below from SAGE Research Methods online to learn more about various research methods and find definitions of research terms. Click on the image of the map to interact with the map online.
Resources for Research Methods
Use the resources below to get more background and information on various research designs and methods.
- Encyclopedia of Survey Research MethodsPaul Lavrakas covers all major facets of survey research methodology, from selecting the sample design and the sampling frame, designing and pretesting the questionnaire, data collection, and data coding, to the thorny issues surrounding diminishing response rates, and more.
- Encyclopedia of Case Study ResearchThis resource for case study research provides a thorough overview of methods and design as guidance for students researchers and professionals who wish to incorporate case studies into a research project.
Independent and Dependent Variables
The following information and examples are from the Encyclopedia of Research Design cited and linked above:
Independent Variables and Dependent Variables
In research design, independent variables are those that a researcher can manipulate, whereas dependent variables are the responses to the effects of independent variables (Salkind, 2010).
Independent variables are predetermined by researchers before an experiment is started. They are carefully controlled in controlled experiments or selected in observational studies (i.e., they are manipulated by the researcher according to the purpose of a study).
The dependent variable is the effect to be observed and is the primary interest of the study (Salkind, 2010).
Consider a study on the relationship between physical inactivity and obesity in young children: The parameter(s) that measures physical inactivity, such as the hours spent on watching television and playing video games, and the means of transportation to and from daycares/schools is the independent variable. These are chosen by the researcher based on his or her preliminary research or on other reports in literature on the same subject prior to the study. The parameter(s) that measure obesity, such as the body mass index, is (are) the dependent variable (Salkind, 2010)
*Salkind, N. J. (2010). Encyclopedia of research design. Thousand Oaks, CA: SAGE Publications, Inc. doi: 10.4135/9781412961288
Internal and External Validity
Types of Validity
Internal Validity
- refers to the accuracy of statements made about the causal relationship between two variables, namely, the manipulated (treatment or independent) variable and the measured variable (dependent)
- internal validity claims are based on the procedures and operations used to conduct a research study, including the choice of design and measurement of variables.
*From Salkind, N. J. (2010). Encyclopedia of research design. Thousand Oaks, CA: SAGE Publications, Inc. doi: 10.4135/9781412961288
External Validity
- refers to the degree to which the relations among variables observed in one sample of observations in one population will hold for other samples of observations within the same population or in other populations. i.e. how general are your results?
*From Frey, B. (2018). The SAGE encyclopedia of educational research, measurement, and evaluation (Vols. 1-4). Thousand Oaks,, CA: SAGE Publications, Inc. doi: 10.4135/9781506326139
Quick guide available from USC School of Social Work: Threats to Internal Validity quick guide