Qualitative research, like all scientific research, consists of comparing ideas with observations. In good research, the ideas are thereby changed—strengthened, weakened, qualified, or elaborated. Criteria for evaluating qualitative research focus both on the process and on the product—that is, on the research methods that are used and on the changed ideas themselves (the interpretation). Many qualitative investigators explicitly reject the possibility of absolute objectivity and truth. The concept of objectivity is replaced by the concept of permeability , the capacity of understanding to be changed by encounters with observations. Investigators argue that we cannot view reality from outside of our own frame of reference. Instead, good practice in research seeks to ensure that understanding is permeated by observation. Investigator bias can be reframed as impermeability (interpretations not permeated by empirical observations). Good practice in reporting seeks to show readers how understanding has been changed. The traditional goal of truth of statements is replaced by the goal of understanding by people . Thus, the validity of an interpretation is always in relation to some person, and criteria for assessing validity depend on who that person is (eg, reader, investigator, research participant). Qualitative research differs from traditional quantitative research on human experience in several ways. Results are typically reported in words rather than primarily in numbers. This may take the form of narratives (eg, case studies) and typically includes a rich array of descriptive terms, rather than focusing on a few common dimensions or scales. Investigators use their (imperfect) empathic understanding of participants' inner experiences as data. Events are understood and reported in their unique context. Materials may be chosen for study because they are good examples rather than because they are representative of some larger population. Sample size and composition may be informed by emerging results (eg, cases chosen to fill …