How can external validity be improved

External validity is threatened when a study does not take into account the interactions of variables in the real world. Internal and external validity are like two sides of the same coin.

You can have a study with good internal validity, but overall it could be irrelevant to the real world. On the other hand, you could conduct a field study that is highly relevant to the real world, but that doesn't have trustworthy results in terms of knowing what variables caused the outcomes that you see.

What are the similarities between internal and external validity? They are both factors that should be considered when designing a study, and both have implications in terms of whether the results of a study have meaning.

Each of these concepts is typically reported in a research article that is published in a scholarly journal. This is so that other researchers can evaluate the study and make decisions about whether the results are useful and valid. The essential difference between internal and external validity is that internal validity refers to the structure of a study and its variables while external validity relates to how universal the results are.

Internal validity focuses on showing a difference that is due to the independent variable alone, whereas external validity results can be translated to the world at large. An 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, and also blinds his research assistants to the groups the students are in during experimentation. A strict study protocol is used that outlines the procedures of the study. Potential confounding variables are measured along with mood, such as the participants socioeconomic status, gender, age, among 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 the study.

An example of a study with good external validity would be in the above example, the researcher also ensured that the study had external validity by having participants use the app at home rather than in the laboratory. Setting up an experiment so that it has sound internal 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 and external validity are high can strong conclusions be made about your results.

Ever wonder what your personality type means? Sign up to find out more in our Healthy Mind newsletter. In the inclusion technique, the role of extraneous variables is considered by including them in the research design and separately estimating their effects on the dependent variable, such as via factorial designs where one factor is gender male versus female.

Such technique allows for greater generalizability but also requires substantially larger samples. In statistical control , extraneous variables are measured and used as covariates during the statistical testing process. During the study, all participants are given an individual mindfulness training and asked to practice mindfulness daily for 15 minutes in the morning.

Since the levels of anxiety decreased between the pre- and post-test, the researcher concludes that all clinical populations can benefit from mindfulness. Threats to external validity Threat Meaning Example Sampling bias The sample is not representative of the population. The sample includes only people with depression. They have characteristics e. History An unrelated event influences the outcomes. Right before the pre-test, a natural disaster takes place in a neighbouring state.

As a result, pre-test anxiety scores are higher than they might be otherwise. Experimenter effect The characteristics or behaviors of the experimenter s unintentionally influence the outcomes.

Participants work extra hard to reduce their anxiety levels during the study as a result. Hawthorne effect The tendency for participants to change their behaviors simply because they know they are being studied. The participants actively avoid anxiety-inducing situations for the period of the study because they are conscious of their participation in the research. Testing effect The administration of a pre- or post-test affects the outcomes.

Because participants become familiar with the pre-test format and questions, they are less anxious during the post-test and recall less anxiety then.

Aptitude-treatment Interactions between characteristics of the group and individual variables together influence the dependent variable. Interactions between certain characteristics of the participants with depression e. The findings are not replicated with people with personality disorders or schizophrenia. The study is repeated with one change; the participants practice mindfulness at night rather than in the morning. The outcomes do not show any improvement this time.

How to counter threats to external validity There are several ways to counter threats to external validity:. The external validity of a study is the extent to which you can generalize your findings to different groups of people, situations, and measures.

I nternal validity is the degree of confidence that the causal relationship you are testing is not influenced by other factors or variables.

You might even be able to map out the degree of proximal similarity among various contexts with a methodology like concept mapping. That is, your external validity ability to generalize will be stronger the more you replicate your study. We send an occasional email to keep our users informed about new developments on Conjoint.

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