IB Psychology SLTopic 5 — Research DesignPaper 1 & 2Core idea~9 min read
Credibility and Transferability
Qualitative research does not use small samples by accident, and it cannot be run twice to see if the same numbers come out. So it is judged by different words. Credibility replaces reliability. Transferability replaces generalisability. Using the right pair for the right kind of study is one of the clearest signs of a strong answer.
📘 What you need to know
Credibility is the qualitative equivalent of reliability: is this account trustworthy and believable?
Transferability is a type of generalisability used with qualitative data.
The aim is not statistical generalisation but findings that resonate with readers through rich detail.
Transferability is easier for common experiences and harder for niche or idiosyncratic ones.
To support it, researchers must fully describe methods, sampling, procedure, analysis and findings.
Triangulation and researcher reflexivity are the two main ways to enhance credibility.
A credible study explains its methods transparently and has been through peer review.
Why the vocabulary changes
A questionnaire with 30 items given to 500 people can be split in half and correlated. An unstructured interview with six people cannot. There is no second half, no score, and no second run. So asking “is it reliable?” makes no sense, and the honest question becomes “can I believe this account, and why?”
The third row is not a formal term but it is the honest version of the trade. Quantitative work buys confidence with numbers; qualitative work buys it with detail.
Transferability
Transferability asks whether the findings of a study can be carried into other populations or contexts outside the ones studied. Crucially, it is the reader who makes that judgement, not the researcher. The researcher’s job is to give them enough information to make it.
That is why good qualitative reports read as if they over-explain. Every stage is described so a reader can decide whether their own situation is similar enough for the findings to be useful.
🧩 What has to be described in full
Methods — the type of interview or observation, and why it was chosen.
Sampling — how participants were found, and why these people.
Procedure — how the study was run, what materials were used, how it was recorded.
Analysis — how the data were analysed and why that approach.
Findings — how they relate to and support the theory being investigated.
When findings transfer well, and when they do not
Age matters too. A study describing a world that has since changed may not transfer to modern contexts, which is the qualitative cousin of temporal validity.
Do not turn this into a criticism by default. A study of a very specific experience is supposed to be specific. The right question is whether the researcher described the context richly enough for a reader to judge the fit, not whether the topic was common enough.
Credibility
Credibility is about whether the account can be believed. Since a qualitative study cannot be replicated to check, trust has to be built into how it was done and how it was reported.
A credible study explains its methods and materials transparently, shows the competence and integrity of the researcher, and has been published after scrutiny such as peer review. None of that guarantees truth, but together they make it much harder for a weak interpretation to pass unnoticed.
Two ways to strengthen credibility
Triangulation
Of data: one dataset checks another, such as interview transcripts against questionnaire responses.
Of researchers: one researcher checks their interpretations with another, agreeing on design, coding or findings.
Agreement across sources makes a conclusion far harder to dismiss.
Disagreement is useful too: it shows exactly where the account is uncertain.
Researcher reflexivity
Honest reflection in the discussion section on both strengths and weaknesses.
Openness about the researcher’s own position and assumptions.
Transparency about limitations increases trustworthiness rather than damaging it.
The reader can see how the conclusions were reached and judge them.
These two terms are worth memorising as a pair with their partners. Reliability goes with credibility. Generalisability goes with transferability. If you can put the right word with the right kind of study, you are already ahead of most answers.
Worked examples
WORKED EXAMPLE
Choose the right criteria
A student writes: “This interview study of eight carers is unreliable because it has not been replicated, and invalid because eight people cannot be generalised.” Correct and improve this evaluation. [4]
Step 1: Identify the wrong rulerReplication and statistical generalisation do not apply to a small qualitative study.Step 2: Swap in the right terms
Ask about credibility instead of reliability, and transferability instead of generalisability.
Step 3: Say what you would actually check
Was there triangulation? Was the researcher reflexive? Were methods, sampling and analysis described fully?
Judge it on credibility and transferabilitythe original evaluation is not wrong about the facts, it is wrong about which criteria matter
WORKED EXAMPLE
Suggest improvements to credibility
A researcher interviews ten teachers and reports four themes. She analysed all the transcripts herself and gives one paragraph describing her method. Suggest two ways to increase the credibility of this study. [4]
Improvement 1: triangulation
A second researcher codes the same transcripts independently and the two interpretations are compared. Researcher triangulation.Improvement 2: reflexivity plus transparency
A fuller account of the method, and a discussion section reflecting on her own assumptions and the limits of the approach.
Say what each achieves
The first checks the interpretation is not one person’s view; the second lets the reader judge how the findings were reached.
Triangulation and reflexive transparencya fuller method section also helps transferability, since readers can judge the fit to their own context
💡 Exam tip
Match the vocabulary to the method. Credibility and transferability for qualitative, reliability and validity for quantitative.
Name the two types of triangulation separately: of data and of researchers.
Say that the reader judges transferability, not the researcher. Very few students know this.
Rich, detailed description is the qualitative equivalent of a large sample. Use that comparison.
Peer review is a legitimate credibility point. It is scrutiny before publication.
Never criticise a qualitative study only for its sample size. It shows you have not understood the criteria.
⚠️ Common mix-up
Credibility and reliability. They answer the same worry with different tools; do not use them interchangeably.
Transferability and generalisability. One is judged by a reader in context; the other is a statistical inference.
Thinking triangulation means using lots of methods. It means checking sources against each other.
Assuming peer review guarantees truth. It is scrutiny, not proof.
Treating “not transferable” as a fatal flaw. Niche topics are often the most valuable ones.
Forgetting that outdated research transfers badly. Context changes, and so does the fit.
Up next: Sampling Techniques and Who Takes Part — the last piece, and the one that decides how far anything in this topic can reach.
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