Validity: A Comparison Between Quantitative and Early Qualitative Perspectives Part 1

In a research landscape dominated by quantitative paradigms, it is important to know how to justify a qualitative perspective. In this first instalment of The Qualitative, I outline the equivalences posited by early pedagogical work on qualitative research, specifically by Lincoln and Guba in their seminal work, Naturalistic Inquiry. I focus on the two categories of validity often cited in quantitative analysis: internal and external validity. This developmental moment in qualitative research is characterised by the adoption of quantitative concepts for qualitative practice. In this era, validity was dealt with in a more or less similar fashion to quantitative methods. 

In this first of a two-part series on validity, I outline internal validity, and juxtapose it with the “naturalistic” response presented by Lincoln and Guba (1985).

This concept refers to the accuracy of causal claims within the population being studied. Internal validity can be improved by identifying and eliminating potential threats, similar to a laboratory experiment.

Common threats to internal validity include the following:

Example: A Clinical Trial of the Effects of Dietary Patterns on Blood Pressure 

Subjects were randomly assigned into two groups, one eating the “control diet” and the other a “combination diet” with initial diet type, sodium intake and body weight controlled. After the experiment, the reductions in blood pressure were accurately attributed to the diet and not to other factors. These findings proved that the experiment has a high internal validity.

The concept of credibility can be viewed as analogous to internal validity. It is an evaluation of whether qualitative findings accurately represent participants’ experiences and realities. It is often pursued through the following:

Example: Member Checks on Patients with Skin Lesions

In ‘Member Checking: A Tool to Enhance Trustworthiness or Merely a Nod to Validation?’ the researchers used participants’ input to further refine their analysis through a novel methodology they call ‘Synthesized Member Checking.’ Although adopting what seems to be a new technique in member checking by incorporating new data through member checks, this study still holds that the value in member checks is in adding to the ‘trustworthiness’ of research results. In spite of being more recent, this study is still a good illustration of the early conception of member checking in the ‘naturalistic’ tradition. 

Appel, L. J., Moore, T. J., Obarzanek, E., Vollmer, W. M., Svetkey, L. P., Sacks, F. M., ... & Harsha, D. W. (1997). A clinical trial of the effects of dietary patterns on blood pressure. New England journal of medicine, 336(16), 1117-1124. https://www.nejm.org/doi/full/10.1056/NEJM199704173361601

Birt L, Scott S, Cavers D, Campbell C, Walter F. Member Checking: A Tool to Enhance Trustworthiness or Merely a Nod to Validation? A Tool to Enhance Trustworthiness or Merely a Nod to Validation? Qualitative Health Research. 2016;26(13):1802-1811. doi:10.1177/1049732316654870

Lincoln, Y.S., & Guba, E.G. (1985). Naturalistic Inquiry. Newbury Park, CA: Sage Publications.

Urry, K., Chur-Hansen, A., & Scholz, B. (2024). From member checking to collaborative reflection: a novel way to use a familiar method for engaging participants in qualitative research. Qualitative Research in Psychology, 21(3), 357–374. https://doi.org/10.1080/14780887.2024.2355972

Kullman, S. M., & Chudyk, A. M. (2025). Participatory Member Checking: A Novel Approach for Engaging Participants in Co-Creating Qualitative Findings. International Journal of Qualitative Methods, 24. https://doi.org/10.1177/16094069251321211 (Original work published 2025)