The criterion of ‘credibility’ in qualitative research is equivalent to which…

Concept

Rigour in any inquiry is judged on four distinct questions: truth value, applicability, consistency and neutrality. Quantitative research answers them with internal validity, external validity, reliability and objectivity; Lincoln and Guba's trustworthiness framework answers the very same four for naturalistic (qualitative) inquiry with credibility, transferability, dependability and confirmability. Equivalence between the two vocabularies is therefore fixed by matching the question each criterion answers, never by matching the words themselves.

Applying it here

Credibility asks whether the researcher's account is a faithful reconstruction of the participants' realities, that is, whether the findings are true of the case actually studied. It is established through a standard set of techniques, all of which work by ruling out alternative readings of the same data:

• prolonged engagement with the setting

• persistent observation of the features most relevant to the question

• triangulation across data sources and methods

• peer debriefing by a disinterested colleague

• negative-case analysis

• member checks with the participants themselves

That is precisely the truth-value question, and among the four conventional quantitative criteria the truth-value question is answered by internal validity, which asks whether the relationship observed really holds within the study once confounding variables and rival explanations have been eliminated. Credibility is therefore the qualitative parallel of internal validity.

Cross-checking the full mapping

Setting out all four criteria side by side shows the correspondence is one-to-one, so once each of the other three quantitative criteria is matched with its own qualitative counterpart, none of them remains available to pair with credibility.

Result

The criterion of credibility in qualitative research is equivalent to internal validity in quantitative research.