ABSTRACT
Ideally, two independent observers will find identical results when examining an identical object. Similarly, an observer should find an identical result when examining the same object for a second (or even third etc.) time. However, disagreement often occurs; disagreement between two examiners is termed inter-observer variability, whereas disagreement within one examiner over time is called intra-observer variability. In general, intra-observer variability is usually somewhat less than inter-observer variability. Disagreement over the interpretation of a test not only occurs in research but is also quite common in everyday clinical medicine. Clinicians often disagree with colleagues about the interpretation of patients’ histories, physical findings or test results, as indicated in the example.
