In the present study, thirty cephalometric films which had been used in three different investigations using almost the same parameters were selected and devided into two groups. Twenty-three parameters in the first group and nine parameters in the second, which were used in two and three investigations respectively, were statistically compared. Paired t test was used in the first group and variance analysis in the second group. In conclusion, a lot of parameters exhibited statistically significant variability, while some of them were not.

Keywords: Roentgenographic Cephalometry, Tracing and Measuring Errors