Threats to Validity in Research

In research, validity refers to the extent to which a study accurately measures what it intends to measure and allows for accurate inferences and generalizations. However, there are various threats to validity that researchers need to be aware of in order to ensure the reliability and credibility of their findings. This article will explore the threats to internal and external validity in research and provide examples of each.

Internal Validity Threats

Internal validity refers to the degree to which a study provides evidence of a causal relationship between variables. The following are some common threats to internal validity:

1. History: Unrelated events occurring during the study can influence the outcomes. For example, in a study investigating the effectiveness of a teaching intervention, changes in the curriculum or teaching methods during the study period could confound the results.
2. Maturation: Changes in participants over time can affect the results. For instance, in a longitudinal study examining the effects of aging on cognitive abilities, natural developmental changes in participants’ cognitive functions could impact the observed outcomes.
3. Instrumentation: Changes in measurement tools or procedures can impact the findings. If different measurement instruments are used at different time points or by different researchers, the results may be inconsistent or biased.
4. Testing: The act of being tested can influence participants’ responses. Participants may become more familiar with the testing procedures or more attuned to the researcher’s expectations, which can alter their behavior or responses.
5. Selection bias: Non-random assignment of participants to groups can introduce bias. If participants are not randomly assigned to different conditions or treatments, there may be pre-existing differences between the groups that affect the outcomes.
6. Regression to the mean: Extreme scores tend to move closer to the average over time. This phenomenon can lead to misleading conclusions if the initial extreme scores are not considered in the analysis.
7. Attrition: Participants dropping out of a study can affect the representativeness of the sample. If certain types of participants are more likely to drop out, the remaining sample may no longer be representative and the results may be biased.

External Validity Threats

External validity refers to the extent to which the findings of a study can be generalized to other populations, settings, or conditions. The following are some common threats to external validity:

1. Interaction of testing and treatment: The combination of pretesting and treatment can affect the results. Pretesting may sensitize participants to the experimental manipulation, leading to different responses compared to individuals who were not pretested.
2. Interaction of selection and treatment: The effects of the treatment may only apply to the specific population selected. If the sample used in the study is not representative of the target population, the generalizability of the findings may be limited.
3. Reactive arrangements: The artificiality of the experimental setting can impact the results. Participants’ behaviors or responses may differ in a controlled laboratory environment compared to real-world settings, affecting the generalizability of the findings.
4. Limited generalizability: Findings may not be applicable to different populations or settings. For example, a study conducted with college students may not yield the same results when applied to a diverse community sample or an elderly population.

In conclusion, threats to validity in research can compromise the internal and external validity of a study. Researchers must carefully consider and address these threats to ensure the accuracy, reliability, and generalizability of their findings.

Sources:

• “Research Design” by Bruce B. Stipak (https://web.pdx.edu/~stipakb/download/PA555/ResearchDesign.html)
• “Internal Validity in Research | Definition, Threats & Examples” by Pritha Bhandari (https://www.scribbr.com/methodology/internal-validity/)
• “Internal vs. External Validity | Understanding Differences & Threats” (https://www.scribbr.com/methodology/internal-vs-external-validity/)

FAQs

What are threats to internal validity in research?

Threats to internal validity in research refer to factors that can undermine the ability to establish a causal relationship between variables within a study. Some common threats to internal validity include history, maturation, instrumentation, testing, selection bias, regression to the mean, and attrition.

How does history impact internal validity?

History can be a threat to internal validity when unrelated events occur during a study that can influence the outcomes. These events may confound the results and make it difficult to determine the true effects of the variables under investigation.

What is selection bias and how does it impact internal validity?

Selection bias occurs when participants are not randomly assigned to different groups or conditions in a study. This can introduce bias and pre-existing differences between the groups, which can affect the internal validity of the study.

What are threats to external validity in research?

Threats to external validity in research pertain to the generalizability of the study findings to other populations, settings, or conditions. Some common threats to external validity include the interaction of testing and treatment, interaction of selection and treatment, reactive arrangements, and limited generalizability.

How does the interaction of testing and treatment impact external validity?

The interaction of testing and treatment can affect external validity when pretesting sensitizes participants to the experimental manipulation. This can lead to different responses compared to individuals who were not pretested, thereby limiting the generalizability of the study findings.

What is limited generalizability and how does it impact external validity?

Limited generalizability refers to the restricted applicability of study findings to different populations or settings. If the sample used in the study is not representative of the target population or the study setting differs significantly from real-world conditions, the external validity of the findings may be compromised.

How does instrumentation affect internal validity?

Instrumentation refers to changes in measurement tools or procedures during a study. These changes can impact the findings and introduce variability or bias in the data, affecting the internal validity of the research.

What is attrition and how does it impact internal validity?

Attrition occurs when participants drop out of a study before its completion. This can affect the representativeness of the sample and introduce biases if certain types of participants are more likely to drop out. Attrition can compromise the internal validity of the research.