So they are very appropriate for exploratory studies because they allow the investigator to decide what to look for. Observation studies can be used to identify and develop explanations of individual differences in task performance. Observational techniques provide data which can be compared and contrasted with information collected by another investigator, or by another method. Disadvantages Real time observation requires trained ergonomists. Observational data is the widest possible form of information, for this reason the effort which must be expended on classification and analysis is considerable.
Direct observation can be an intrusive technique.
Therefore the investigator must estimate whether the type of observation selected will significantly alter the task under study. Observational situations which produce rich context data are rarely the ones which produce precise and controlled data. So data will be incomplete, inconsistent and sometimes unusable Observational techniques cannot provide information about underlying thought-processes, and so they will be of very little use for highly cognitive activities. The equipment needed for producing high quality observational data can be expensive and difficult to install, and video recording followed by later analysis is time-consuming. At the simplest level passive observation, where the person conducting the observation quietly observes and records the user activity, can be used to record some details of the processes which the user undertakes.