title: A study of the factors causing differences in the relative variability of linear radiographic cephalometric measurements.
abstract: Certain factors causing variation of linear radiographic cephalometric measurements were evaluated using the regression analysis. The material of the study consisted of data from three earlier investigations and included 73 measurements of four separate samples of children and young adults. Approximately 75% of the variation of the variation coefficient (V) could be attributed to the variation in the length of the measurements (means) and thus mainly to the mathematic properties of V. Thus, differences in the relative variation did not always indicate differences in the absolute variation (SD). Two factors were extracted that had an increasing effect upon the variability--the location of the reference points on an osseous contour and the location of the reference points (one or both) in the mandible. The great variability of the reference points located on osseous contours was probably caused by local changes in bone configurations, and the great variability of the measurements involving the mandible probably indicated some specific growth changes in the size, form, and rotation movements of this bone. In clinical use such reference points that include relevant information only and that could be fixed by consistent features of the local morphology should be preferred.
mesh_terms: D000293:Adolescent; D000328:Adult; D002508:Cephalometry / Q000379:methods*; D002648:Child; D006801:Humans; D008297:Male; D008334:Mandible / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D008437:Maxilla / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D011859:Radiography; D012044:Regression Analysis; D012886:Skull / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D013223:Statistics as Topic