Formal observation refers to the precise, highly controlled methods that take place in a laboratory setting, while informal observation is a more casual observation of the surrounding environment. Anthropologists and others in the soft sciences often make use of informal observation, while hard sciences generally require more stringent methods of empirical assessment.
Audience Dialogue describes formal and informal observations as two equally crucial components of information gathering. The main goal behind any type of observation is to gather data about the subject or subjects being observed. Informal observation can be as simple as watching people from a park bench and noticing trends or patterns in their appearance and clothing.
The Cleremont College of Biology delves into the nature of formal observation and notes how crucial it is to ensure that all observations are made with the utmost objectivity. Informal observations are subjective to a degree, but all measures are taken to ensure that a formal observation is without subjectivity. To do this, most researchers set up a series of controls that allow them to watch the chosen subject with as little interference and distraction as possible. This ensures that any information gathered is true to the subject's usual behavior and not changed by the observer.