Observation is a method of collecting data without using instruments by actively acquiring information through the senses. There are different types of observation including controlled, non-controlled, participant, non-participant, formal, and informal. Observation has merits such as being a flexible method that can produce both qualitative and quantitative data on individuals and groups. However, it also has limitations such as being labor intensive, difficult to get trained observers, and inability to establish causal relationships or study past behavior.