A qualitative calculus based on signs was first developed by economists to overcome one major difficulty: we often face a lack of quantitative data. A number of methods such as comparative statics were proposed to solve qualitative-model-based problems. A new interest has recently arisen in qualitative methods as applied to process control, control theory, and artificial intelligence (the autho...

Gummesson contends that quantitative techniques are mostly used to try to pinpoint causality, usually between two or a few variables where the independent and dependent variables are defined. According to Milliken, in reviewing the management literature, especially marketing management, it is evident that little attention has been paid to qualitative research in the discipline. Varki et al. hol...