Whether or not a given study has the possibility of causing harm to participants:
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Published on May 1, 2020 by Pritha Bhandari. Revised on October 10, 2022. geInternal validity is the extent to which you can be confident that a cause-and-effect relationship established in a study cannot be explained by other factors. In other words, can you reasonably
draw a causal link between your treatment and the response in an experiment? 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. Once they arrive at the laboratory, the treatment group participants are given a cup of coffee to drink, while control group participants are given water. You also give both groups memory tests. After analyzing the results, you find that the treatment group performed better than the control group on the memory test. Can you conclude that drinking a cup of coffee improves memory performance? For your conclusion to be valid, you need to be able to rule out other explanations for the results. How to check whether your study has internal validityThere are three necessary conditions for internal validity. All three conditions must occur to experimentally establish causality between an independent variable A (your treatment variable) and dependent variable B (your response variable).
In the research example above, only two out of the three conditions have been met.
Because you assigned participants to groups based on the schedule, the groups were different at the start of the study. Any differences in memory performance may be due to a difference in the time of day. Therefore, you cannot say for certain whether the time of day or drinking a cup of coffee improved memory performance. That means your study has low internal validity, and you cannot deduce a causal relationship between drinking coffee and memory performance. Trade-off between internal and external validityExternal validity is the extent to which you can generalize the findings of a study to other measures, settings or groups. In other words, can you apply the findings of your study to a broader context? There is an inherent trade-off between internal and external validity; the more you control extraneous factors in your study, the less you can generalize your findings to a broader context. Research exampleIn your study of coffee and memory, the external validity depends on the selection of the memory test, the participant inclusion criteria, and the laboratory setting. For example, restricting your participants to college-aged people enhances internal validity at the expense of external validity – the findings of the study may only be generalizable to college-aged populations.Threats to internal validity and how to counter themThreats to internal validity are important to recognize and counter in a research design for a robust study. Different threats can apply to single-group and multi-group studies. Single-group studiesResearch example (single-group) A research team wants to study whether having indoor plants on office desks boosts the productivity of IT employees from a company. The researchers give each of the participating IT employees a plant to place by their desktop for the month-long study. All participants complete a timed productivity task before (pre-test) and after the study (post-test).
How to counter threats in single-group studiesAltering the experimental design can counter several threats to internal validity in single-group studies.
Multi-group studiesResearch example (multi-group)A researcher wants to compare whether a phone-based app or traditional flashcards are better for learning vocabulary for the SAT. They divide 11th graders from one school into three groups based on baseline (pre-test) scores on vocabulary. For 15 minutes a day, Group A uses the phone-based app, Group B uses flashcards, while Group C spends the time reading as a control. Three months later, post-test measures of vocabulary are taken.
How to counter threats in multi-group studiesAltering the experimental design can counter several threats to internal validity in multi-group studies.
Frequently asked questions about internal validityCite this Scribbr articleIf you want to cite this source, you can copy and paste the citation or click the “Cite this Scribbr article” button to automatically add the citation to our free Citation Generator.
Is this article helpful?You have already voted. Thanks :-) Your vote is saved :-) Processing your vote... What are the possible harm to the research participants?There are various types of harm that can occur while participating in a study such as: psychological harm, physical harm, legal harm, social harm, and economic harm.
What is risk of harm in research?A risk is a potential harm or injury associated with the research that a reasonable person would be likely to consider significant in deciding whether or not to participate in the study. The concept of risk includes discomfort, burden, or inconvenience a subject may experience as a result of the research procedures.
Which type of study is most likely to enable generalization of the findings?Correlational studies allow researchers to make broad generalizations. Case studies allow researchers to consider various causes.
Is important to obtain before starting a research study to ensure people know they are involved in the study?Informed consent is crucial in research as it ensures individuals have an informed choice about whether to participate in a research study. In the United States, the requirements for obtaining informed consent from research participants are stipulated by several regulations and policies.
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