Interpretivists argue that qualitative methods are high in validity as they give a better level of understanding
Semi/un structured interviews help build rapport by creating a trusting, fluid, conversational style where they are more likely to give longer, detailed, truthful answers. Also allows ideas to emerge that the interviewer may not have thought to ask.
Open questions increase validity as it allows them to talk at length, giving more detailed and nuanced information. Also allow the interviewee to ask for clarification, and so the interviewer can explain a question or term further. This clarification ensures that the data produced reflects a better truth.
Observation increases validity as the researcher sees them in the natural environment that offers a better version of the truth than a formal interview setting, particularly if covert.
Participant observation helps achieve verstehen, thus increasing validity, as they begin to see life from the perspective of the respondents and empathise.
Longitudinal studies improve validity as they show a long period, rather than a snapshot.