When I was working on my master of arts in education two decades ago, my mentors introduced me to qualitative research methods, especially interviewing. One of the lessons I learned early in that work was that the term and concepts we usually apply to the quality of quantitative data do not accurately describe the expectation we have of qualitative researchers. Terms like validity, reliability, and objectivity cannot be applied to qualitative researcher who are likely to play and active role in the the data collection. An article written by Marie C. Hoepfl became one of the references I would use to both ensure my work was high quality and to describe good qualitative data to others. The work is has been available online since its first appearance, and the original html version has ben replaced by a much more readable PDF version.
It is still my primary source for understanding qualitative research.
Hoepfl, Marie. 1997. Choosing Qualitative Research: A Primer for Technology Education Researchers. Journal of Technology Education 9(1).