Key Difference – Internal vs External Validity
In research, validity refers to the approximate truth of propositions, inferences, or conclusions. Internal and external validity are two parameters used to evaluate the validity of a research study or procedure. The main difference between internal and external validity lies in their areas of focus: internal validity is concerned with the connection between variables, while external validity is concerned with the generalization of results.
Key Takeaways
- Internal validity is the extent to which a researcher can claim that no other variables except the one being studied caused the result.
- External validity is the extent to which the results of a study can be generalized to the world at large.
- Good research studies are designed to minimize the possibility that any variables other than the independent variable affect the dependent variable, thereby increasing internal validity.
What is Internal Validity?
Most research studies attempt to show the relationship between two variables: dependent and independent variables, that is, how one variable (independent variable) affects another (dependent variable). If the researcher can state that the independent variable causes the dependent variable, they have made the strongest statement in research.
Internal validity is the extent to which the researcher can make the claim that no other variables except the one being studied caused the result. For example, if studying the variable of self-study and exam results, it should be possible to say that no other variable (teaching methods, extra tuition, intelligence levels, etc.) causes good exam results.
When there is a good chance that other variables can affect the result, the study has low internal validity. Good research studies are always designed in a way that tries to minimize the possibility that any variables other than the independent variable affect the dependent variable.
Internal validity is mostly relevant to studies that try to establish a causal relationship; they are not relevant in observational and descriptive studies. However, internal validity may be relevant to studies that evaluate the effects of a certain program or interventions.
What is External validity?
External validity is about the generalization of a conclusion of a research study. More specifically, it is the extent to which the results of a study can be generalized to the world at large.
A goal of a research study is to make inferences about the way things work in the real world based on the results of a study. For example, generalizing the results of a study done on a sample population to the population as a whole. Similarly, applying the results of research done with a few students to a real-world setting like a school. However, a researcher cannot make these inferences without external validity. If the external validity of a study is low, the results cannot be applied to the real world, meaning the research study will not reveal anything about the world outside the study.
Researchers use strategies like sampling models and proximal similarity models to increase the external validity of their studies.
What is the difference between Internal and External Validity?
Definition:
Internal Validity: Internal validity is the extent to which the researcher can make the claim that no other variables except the one being studied caused the result.
External Validity: External validity is the extent to which the results of a study can be generalized to the world at large.
Area:
Internal Validity: Internal validity is concerned with the connection between variables.
External Validity: External validity is concerned with the generalization of results.
