In qualitative research, internal and external validity refer to the trustworthiness and applicability of your findings, albeit interpreted differently than in quantitative studies where the concepts originated.
While a common definition states that **internal validity is the degree of confidence that the causal relationship you are testing is not influenced by other factors or variables**, and **external validity is the extent to which your results can be generalized to other contexts**, these definitions are adapted for the unique goals and methods of qualitative inquiry. Qualitative research typically does not aim to establish causal links in a testable, experimental way or to generalize findings statistically to large populations. Instead, it focuses on understanding experiences, meanings, and contexts in depth.
Here's how these concepts are understood and addressed in the qualitative paradigm:
## Internal Validity (Credibility)
In qualitative research, the concern similar to internal validity is often referred to as **credibility**. It asks: How confident are we that the findings accurately represent the participants' reality, experiences, or perspectives? Are the results a faithful depiction of the phenomenon being studied from the insider's point of view?
Instead of controlling variables as in an experiment, qualitative researchers enhance credibility through rigorous methods that ensure the findings are plausible and believable to those who experienced the phenomenon.
**Strategies to Enhance Credibility:**
* **Prolonged Engagement:** Spending sufficient time in the field to build rapport, learn the culture, and test for misinformation.
* **Persistent Observation:** Identifying salient characteristics of the situation being studied and focusing on aspects relevant to the research question.
* **Triangulation:** Using multiple sources of data (e.g., interviews, observations, documents), multiple methods (e.g., interviews and focus groups), multiple researchers, or multiple theories to cross-check findings.
* **Member Checking:** Taking data, interpretations, and conclusions back to the participants to confirm their accuracy and resonance with their experiences.
* **Rich, Thick Description:** Providing detailed accounts of the research context, participants, and findings, allowing readers to immerse themselves in the setting and judge the credibility of the findings for themselves.
* **Peer Debriefing:** Discussing the research process and findings with a peer who is not involved in the study to challenge assumptions and interpretations.
## External Validity (Transferability)
The concept akin to external validity in qualitative research is **transferability**. Instead of asking if results can be statistically generalized to a population, transferability asks: Can the findings be applied or transferred to other settings or groups? Are the results relevant or meaningful in contexts beyond the specific study?
Qualitative researchers do not seek to generalize results broadly in the quantitative sense. Instead, they aim to provide enough detail about the study context and findings that a reader can determine if the findings are relevant to their own situation or context.
**Strategies to Enhance Transferability:**
* **Thick Description:** Providing detailed descriptions of the study setting, participants, sampling strategies, data collection methods, and the findings themselves. This allows readers to assess the similarity between the study context and their own, and thus judge the potential applicability of the findings.
* **Purposive Sampling:** Selecting participants and settings that are information-rich and relevant to the research question, often aiming for variation or specific characteristics rather than representativeness.
* **Developing Theoretical Constructs:** Moving from specific observations to more abstract concepts or theories that might be relevant in other situations.
## Comparing Internal/External Validity (Quantitative) vs. Credibility/Transferability (Qualitative)
While the terminology differs and the approaches vary significantly, the underlying concerns about the quality and applicability of research findings are shared.
| Concept | Quantitative Research | Qualitative Research |
| :---------------- | :----------------------------------------------------- | :------------------------------------------------------ |
| **Internal Focus** | **Internal Validity:** Confidence in causal links. | **Credibility:** Accuracy of findings from participant view. |
| **External Focus** | **External Validity:** Generalizability to populations. | **Transferability:** Applicability to other contexts. |
| **Goal** | Establish cause-effect relationships, generalize. | Understand meaning, experience, context; provide insight. |
| **Methods** | Control variables, experiments, statistical analysis. | Rich description, triangulation, member checking, etc. |
In summary, while the reference accurately defines validity in a quantitative experimental context (where validity *depends on your experimental design*), qualitative researchers adapt these core concerns about trustworthiness and applicability, using terms like credibility and transferability and employing different methodological strategies to ensure their findings are robust within their specific aims.
