how long does a formal observation last?
<answer> Forty-five minutes <context> A formal observation must be a minimum of forty-five minutes in length. It may be divided into segments equal to forty-five minutes with the mutual consent of the teacher and appraiser.o. An appraiser scores the criteria that are observed when conducting a formal 45-minute observation. If the appraiser does not have enough evidence to score all criteria, he or she may leave the undocumented criteria blank.