An excellent piece on this (though there are plenty of manuals on qualitative data collection and analysis) is by Lincoln and Guba. They suggest that ‘conventional’ rigor addresses internal validity (which they take as ‘truth value’), external validity, consistency/replicability and neutrality. (The extent to which quantitative research in the social sciences fulfils all these criteria is another debate for another time.) They highlight the concept of ‘trustworthiness’ – capturing credibility, transferrability, dependability and confirmability – as a counterpart to rigor in the quantitative social sciences. It’s a paper worth reading.Plus purposeful pursuit of disconfirming evidence.
The author is arguing that qualitative evidence should be incorporated more systematically in pursuit of knowledge and truth. She doesn't shrink from the historical shortcomings and challenges associated with qualitative data.
Regardless of what types of data are being collected, representativeness is important to being able to accommodate messiness and heterogeneity. If a research team uses stratification along several to select its sample for quantitative data collection (or intends to look at specific heterogeneities/sub-groups for the analysis), it boggles my mind why those same criteria are not used to select participants for qualitative data. Why does representativeness so often get reduced to four focus groups among men and four among women? Equally puzzling, qualitative data are too often collected only in the ‘treated’ groups. Why does the counterfactual go out the window when we are discussing open-ended interview or textual data?While the author sets out to advocate a particular position, include more qualitative information in experiments, her article is actually a reasonably good critique of all data collection (whether quantitative or qualitative) and how knowledge is short changed and misled by poorly designed experiments.
Similarly, qualitative work has a counterpart to statistical power and sample size considerations: saturation. Generally, when the researcher starts hearing the same answers over and over, saturation is ‘reached.’ A predetermined number of interviews or focus groups does not guarantee saturation. Research budgets and timetables that take qualitative work seriously should start to accommodate that reality. In addition, Lincoln and Guba suggest that length of engagement – with observations over time also enhancing representativeness – is critical to credibility. The nature of qualitative work, with more emphasis on simultaneous and iterative data collection and analysis can make use of that time to follow up on leads and insights revealed over the study period.
In general, if we want to talk about creating credible, causal narratives that can be believed and that can inform decision-making at one or more levels, we need to talk about (a) careful collection of all types of data and (b) getting better at rigorously analysing and incorporating qualitative data into the overall ‘narrative’ for triangulating towards the ‘hard’ truth, not equating qualitative data with anecdotes.