observer variation

observer variation,

n the failure by the observer to measure or identify a phenomenon accurately, which results in an error. The observer may miss an abnormality or use faulty techniques, such as incorrect measurement or misinterpretation of the data. Two types are interobserver variation (the amount observers vary from one another when reporting on the same material) and intraobserver variation (the amount one observer varies between observations when reporting more than once on the same material).