Key Difference – Internal vs External Validity
In the field of research, validity refers to the approximate truth of propositions, inferences, or conclusions. Internal and external validity are two parameters that are used to evaluate the validity of a research study or procedure. The key difference between internal and external validity is that internal validity is the extent to which the researcher is able to make the claim that no other variables except the one he is studying caused the result whereas external validity is the extent to which results of a study can be generalized to the world at large.
What is Internal Validity?
Most research studies attempt to show the relationship between two variables: dependent and independent variables, i.e., how one variable (independent variable) affects another (dependent variable). If the researcher can state that the independent variable causes the dependent variable, he has made the strongest statement in research.
Internal validity is the extent to which the researcher is able to make the claim that no other variables except the one he is studying caused the result. For example, if we are studying the variable of self-study and the result of exam results, we should be able to say that no other variable (teaching methods, extra tuition, intelligent levels, etc.) causes good exam results.
When there’s a good chance that other variables can affect the result, the study has a 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. In studies like this, researcher may be interested in knowing whether the program made a difference; for example, if a researcher is testing out a new teaching methodology, he may want to know whether it increased the results, but he’d also want to make sure that it is his new teaching methodology and not some other factors that made the difference. This is where internal validity comes into play.
What is External validity?
External validity is about the generalization of a conclusion of a research study. To be more specific, it is the extent to which 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 work based on the results of a study. For example, we can generalize the results of a study done on a sample population to the population as a whole. Similarly, we can use the results of research done with few students and apply it to a real-world setting like school. However, a researcher cannot make these inferences without external validity. If the external validity of a study is low, the results of a study cannot be applied to the real world, which means that the research study won’t reveal anything about the world outside the study.
Researchers use strategies like sampling model and proximal similarity model 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 is able to make the claim that no other variables except the one he is studying caused the result.
External Validity: External validity is the extent to which 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.
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