Internal validity is a measure of how well a study is conducted (its structure) and how accurately its results reflect the studied group. Show
External validity relates to how applicable the findings are in the real world. These two concepts help researchers gauge if the results of a research study are trustworthy and meaningful. Internal Validity
External Validity
What Is Internal Validity in Research?Internal validity is the extent to which a research study establishes a trustworthy cause-and-effect relationship. This type of validity depends largely on the study's procedures and how rigorously it is performed. Internal validity is important because once established, it makes it possible to eliminate alternative explanations for a finding. If you implement a smoking cessation program, for instance, internal validity ensures that any improvement in the subjects is due to the treatment administered and not something else. Internal validity is not a "yes or no" concept. Instead, we consider how confident we can be with study findings based on whether the research avoids traps that may make those findings questionable. The less chance there is for "confounding," the higher the internal validity and the more confident we can be. Confounding refers to uncontrollable variables that come into play and can confuse the outcome of a study, making us unsure of whether we can trust that we have identified the cause-and-effect relationship. In short, you can only be confident that a study is internally valid if you can rule out alternative explanations for the findings. Three criteria are required to assume cause and effect in a research study:
Factors That Improve Internal ValidityTo ensure the internal validity of a study, you want to consider aspects of the research design that will increase the likelihood that you can reject alternative hypotheses. Many factors can improve internal validity in research, including:
Internal Validity ThreatsJust as there are many ways to ensure internal validity, there is also a list of potential threats that should be considered when planning a study.
What Is External Validity in Research?External validity refers to how well the outcome of a research study can be expected to apply to other settings. This is important because, if external validity is established, it means that the findings can be generalizable to similar individuals or populations. External validity affirmatively answers the question: Do the findings apply to similar people, settings, situations, and time periods? Population validity and ecological validity are two types of external validity. Population validity refers to whether you can generalize the research outcomes to other populations or groups. Ecological validity refers to whether a study's findings can be generalized to additional situations or settings. Another term called transferability refers to whether results transfer to situations with similar characteristics. Transferability relates to external validity and refers to a qualitative research design. Factors That Improve External ValidityIf you want to improve the external validity of your study, there are many ways to achieve this goal. Factors that can enhance external validity include:
External Validity ThreatsExternal validity is threatened when a study does not take into account the interaction of variables in the real world. Threats to external validity include:
While rigorous research methods can ensure internal validity, external validity may be limited by these methods. Internal Validity vs. External ValidityInternal validity and external validity are two research concepts that share a few similarities while also having several differences. SimilaritiesOne of the similarities between internal validity and external validity is that both factors should be considered when designing a study. This is because both have implications in terms of whether the results of a study have meaning. Both internal validity and external validity are not "either/or" concepts. Therefore, you always need to decide to what degree a study performs in terms of each type of validity. Each of these concepts is also typically reported in research articles published in scholarly journals. This is so that other researchers can evaluate the study and make decisions about whether the results are useful and valid. DifferencesThe essential difference between internal validity and external validity is that internal validity refers to the structure of a study (and its variables) while external validity refers to the universality of the results. But there are further differences between the two as well. For instance, internal validity focuses on showing a difference that is due to the independent variable alone. Conversely, external validity results can be translated to the world at large. Internal validity and external validity aren't mutually exclusive. You can have a study with good internal validity but be overall irrelevant to the real world. You could also conduct a field study that is highly relevant to the real world but doesn't have trustworthy results in terms of knowing what variables caused the outcomes. Examples of ValidityPerhaps the best way to understand internal validity and external validity is with examples. Internal Validity ExampleAn example of a study with good internal validity would be if a researcher hypothesizes that using a particular mindfulness app will reduce negative mood. To test this hypothesis, the researcher randomly assigns a sample of participants to one of two groups: those who will use the app over a defined period and those who engage in a control task. The researcher ensures that there is no systematic bias in how participants are assigned to the groups. They do this by blinding the research assistants so they don't know which groups the subjects are in during the experiment. A strict study protocol is also used to outline the procedures of the study. Potential confounding variables are measured along with mood, such as the participants' socioeconomic status, gender, age, and other factors. If participants drop out of the study, their characteristics are examined to make sure there is no systematic bias in terms of who stays in. External Validity ExampleAn example of a study with good external validity would be if, in the above example, the participants used the mindfulness app at home rather than in the laboratory. This shows that results appear in a real-world setting. To further ensure external validity, the researcher clearly defines the population of interest and chooses a representative sample. They might also replicate the study's results using different technological devices. A Word From VerywellSetting up an experiment so that it has both sound internal validity and external validity involves being mindful from the start about factors that can influence each aspect of your research. It's best to spend extra time designing a structurally sound study that has far-reaching implications rather than to quickly rush through the design phase only to discover problems later on. Only when both internal validity and external validity are high can strong conclusions be made about your results. What type of validity is most concerned with whether there is a casual relationship?Internal validity makes the conclusions of a causal relationship credible and trustworthy. Without high internal validity, an experiment cannot demonstrate a causal link between two variables.
What type of validity is most concerned with whether the results can be generalized to other persons places and times?External validity is the extent to which you can generalize the findings of a study to other situations, people, settings and measures. In other words, can you apply the findings of your study to a broader context? The aim of scientific research is to produce generalizable knowledge about the real world.
Which of the following forms of validity is most related to establishing a cause effect relationship in a study?Internal validity is the extent to which a research study establishes a trustworthy cause-and-effect relationship.
What type of research highlights causality allowing the cause to be separated from the effect?The laboratory experiment is traditionally considered the “gold standard” in psychology research. This is because only laboratory experiments can clearly separate cause from effect and therefore establish causality.
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