Posted on: 9th Apr 2020 1021 Views

Internal Vs External Validity in Research

Validity gets split up into two categories internal and external validity at the time of testing the relationship between cause and effect. Students studying master’s or undergraduate courses have confusion between internal vs external validity. Our professional is explaining the difference between internal and external validity.

Internal Vs External Validity in Research

Difference between internal and external validity

Internal validity is a level up to which causal relationships between variables are trustworthy. On the other hand, external validity is the degree up to which the research outcome applies to other situations.

Another difference between the internal vs external validity is that internal validity emphasizes the relationship between different variables of the study. However, external validity focuses on the universality of the research outcomes.

  • Note: It is the experimental design that helps in determining both the internal and external validity of the research. It is very much important for you to consider measurement validity. These tactics will help you in making sure the validity of tools or methods which you have used for performing research.

Now let’s look at the difference between internal and external validity in detail.

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Basis Internal validity External validity
Meaning  Internal validity is the level up to which an experiment or research is free from errors.
Errors might include variations in measurement because of the independent variable.
It is a degree up to which outcomes of the research could be inferred to the real world on a large scale.
Emphasizes on  It mainly emphasizes controlling extra variables.  It mainly focuses on naturalness. External validity is mainly concerned with the applicability of the results.
Things which it measures  Internal validity helps in measuring the accuracy of experiments.  External validity is helpful in measuring the causal relationship between different variables of the study.
Identifies  It helps in measuring the strength of methods that researchers use for performing research. It assists in ensuring that research results apply to the real world.
Description Level up to which conclusion is warranted. Extent up to which research is warranted for generalizing the outcome.
Use You can use internal validity to provide an alternative explanation of research outcomes.  The researcher mainly uses external validity for the generalization of results.

Let’s develop an understanding of the difference between factors affecting internal and external validity.

Internal vs. external validity threats differences










It can be defined as a situation where changes in variables can take place because of alteration in the third variable.

Historical events: It means that changes in the situation can have a great influence on research outcomes.

Testing: This includes the effect of testing continuously and the use of the same measures on participants.

Instrumentation: It means the influence of the instrument which the researcher uses on the response provided by participants during the study.

Situational factors: changes in time, location can have a significant influence on the generalization of research findings.


Pre and post-test effect: It refers to the situation when you perform pre or post-test. As the changes in the situation can have a significant influence on research outcomes.

Sample features: Few characteristics of the population from where the sample has been taken can influence the external validity of the research.

People whom you have select as participants might limit the generalization of research findings.
Selection bias: Biasness in making the selection of participants by the researcher can create a threat to the external validity of the research.


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Comparison between the techniques of improving internal  and external validity














Factors that help in improving

 The  factors which help in improving the internal validity are :

Randomization: It is the technique that includes assigning participants with treatment on a random basis. As per this technique you should make sure the elimination of biases between groups.

Random selection: This technique involves the selection of participants for the researcher using a random sampling technique. After selecting participants, you need to make sure that it represents a population.

Blinding: It is a kind of knowledge biases. Researchers should be aware of the interventions they are receiving. It is one of the best techniques to avoid knowledge biases.

Experimental manipulation: This technique involves the manipulation of independent variables.

The factor which helps in improving the external validity are:

Inclusion and exclusion criterion: In this technique, you need to make sure that you have properly defined the population. Psychological realism: As per this technique you need to make sure that Participants are being able to gain experience of real events that have taken place during the study.

Replication: It includes performing research again by making different arrangements. You can use meta-analysis for measuring the reliability of the influence which the independent variable has on the dependent variables of the study.

Field experiments: This technique including the execution of investigation outside the laboratory setting.


From the above article, it has been summarised that experimental research design helps judge the internal and external validity of the research. Another fact which has been found from an investigation is that internal validity is a very crucial requirement which you need to fulfill. Whereas, external validity is the universality of the results cornerstone of experimental research design.

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