The reproducibility and repeatability of the Wits analysis.

Since the introduction of the Wits analysis, the validity of the method has been questioned, as the functional occlusal plane in particular has been cited as a major source of error. This may be either subjectively placed or defined by existing cephalometric methods. A study is therefore reported of the repeatability (intraobserver comparison) and reproducibility (interobserver comparison) of the Wits assessment on the basis of a double series of tracings by each of two observers. No statistically significant difference was found for the repeatability of distance AO-BO by either observer, but interobserver repeatability was less satisfactory, and the mean values varied by approximately 75%. It was also found that the highest single error between two series of tracings was 3.1 mm (observer A) and 5.8 mm (observer B).