Qualitative research may offer the only alternative when hypotheses do not translate well into quantitative terms. One instance occurs when a new theory cannot provide well-defined hypotheses or its constructs have no adequate measures.
A more common problem occurs when the natural social setting provides the only or best location for research but will not permit the usual standardized measures. For example the actors under study may change their behaviour or expel the researcher when they become aware of the measurement process. In such cases, the qualitative approach may serve well.