There is an opposition between studying social groups not accessible through established means of sociological research and using research methodologies based on intensive, detailed, data collection strategies. There is also a clear distinction between ascending and descending methods in the case of classification analysis; the classes obtained by HA classification are called polythetic classes. Cross-classification analysis is the Cartesian crossing of two automatic classification analysis and snowball sampling are compatible in ascending methodology and have been used to study drug abusing behavior in several European cities. When conducting this sort of analysis, researchers must be aware of possible random error or sampling error, sample bias, and response bias which are the major sources of inaccuracy in data collection. 31 references