## 3 Results
### Results--Operating Times
It can be seen from the diagrams that the operating times shorten with increasing levels of experience. It is also noticeable that the use of the navigation device does not afford a time advantage for any physician's position. In terms of the mean operating times, this is because the times must be weighted according to the physician's position in order to obtain an overall average. The uneven number of cases in the two groups, and the non-symmetrical frequency distribution, also play a role. The longer operating times can be explained in the case of junior doctors with less surgical experience or routine practice exercises. However, it is surprising that the operating times are longer for specialists than for junior doctors. It is also noticeable that junior doctors and specialists operate rather infrequently with a navigation system. In five years, 22 junior doctors performed 136 operations without a navigation device and 34 with one. The pattern is similar for specialists; seven specialists were responsible for 179 operations without a navigation device and 33 operations with one. The operating times are similar for junior doctors (87 min without and 93 min with navigation) and specialists (93 min without and 114 min with navigation). Greater surgical experience is clearly reflected in the median operating times for the consultants and the head of the department. In non-navigated operations, those consultants with a median of 67 min, and the head of the department with 49 min, are faster than the corresponding overall median of 72 min. For procedures in which the navigation device is used, the consultants require a median of 72 min, the head of the department, 57 min. Their operations take longer with the navigation device: the consultants require 5 min longer with navigation, the head of the department, 8 min longer. Figure 6: Mean time without and with navigation with standard deviation (SD); (JNR: Junior Doctor; SP: Specialist; CON: Consultant; HD: Head of Department). Figure 7: Median time without and with navigation, with interquartile range (IQR). Table 7 reveals that two physicians in a particular position usually performed more than 50% of the navigated operations. Among the junior doctors, JNR3 and JNR17 operated most frequently, with 6 and 14 procedures, respectively. In the group of specialists, it is SP2 and SP3 who are most frequently involved, with 7 and 14 operations, respectively; among the consultants, it is CON7 and CON9, with 23 and 28 procedures, respectively. The head of the department performed 183 navigated operations. These physicians have the most experience with the navigation device and, therefore, have the greatest influence on the analysis. When operation numbers without navigation are added, these doctors usually performed the most operations in their position group and, hence, have the most experience with sinus surgery. Comparing these physicians among themselves shows that only SP3 is faster with the navigation device, by about 1 min, with a median incision-suture time of 112 min. The two consultants require a median of more than 20 min longer per operation when using navigation. Table 6 shows the calculation of incision-suture times when considering these selected physicians. This shows that, while the overall mean times of the two groups match, the median times change for a comparable number of operations. For 310 non-navigated operations, the mean operating time is now 74.6 min and has, hence, become shorter. Navigated operations last 73.8 min on average, for a total of 275 operations. Conversely, the navigated operations with the selected physicians now lasted 10 min longer in the overall median. The overall median of navigated operations remains the same as in Table 5, at 69 min. The median time of 72 min falls to 59 min for those operations without navigation.