An observational study is a technique, where researchers observe the behavior in systematic manner without any influence. Researchers record the behavior or use the rating method. In this method consumers may unaware that they are being monitored.
Compared with other methods, observational research offers the major advantage that the information is objective and does not depend on respondent co-operation and memory. It removes from consideration, therefore, all the usual concerns about the effect of the research process depend itself on the information obtained.
However, its typical limitations consist in its incapability exploring the actual causes of behaviors.
But for a large number of respondent set, this method is so effective.