Qualitative research designs tend to be fluid, and thus avoid closing topics of inquiry too early
(Spradley 1980). In a typical quantitative model, an instrument used to measure program effects is
almost never changed. The program may go through modifications, or the evaluators may discover
other indicators of program effects, but the measurements must remain consistent throughout the
testing periodisi, or risk threats to validity. For that reason, these models fail to locate unintended
outcomes of programs (Koppelman, 1983). in contrast, qualitative measurement instruments are
often open-ended or semi-structured, and can allow for new information, new indicators, or new
meanings that will add depth and holism to the evaluation.