## 3 Results
### Trend Change Index  
The diagrams below (Figure 5A-D) present the medians of the TCI value. Table 1 presents the \(p\)-values obtained for the comparison of the TCI values. In the diagram presenting the TCI values for individual measurements (Figure 5A), one can observe that the TCI value obtained for the measurements using the oscillating scenery at a frequency of 1.4 Hz was at a similar level to the OE and CE measurements. The TCI values in the case of disturbances at a frequency of 0.7 Hz were lower than the values obtained in other measurements. The data distribution was also noticeably higher. The comparison of the OE and CE measurements did not reveal any statistically significant differences. Statistically significant differences were observed when comparing the OE test in a real-life environment to measurements in the virtual environment for the case of the oscillating scenery at a frequency of 0.7 Hz--both before (0.7_before) and after (0.7_after) the change in frequency. However, in the case of the CE test, statistically significant differences did not occur except for the oscillating scenery experiment at a frequency of 0.7 Hz after the change in frequency (0.7_after). When comparing the tests conducted in VR,  
Figure 4: (**A**,**B**). Stabilographic values in the time domain (EO—eyes opened, EC—eyes closed, 0.7_—first 15 s of measurement in the oscillating scenery at a frequency of 0.7 Hz, 0.7_—second 15 s of measurement in the oscillating scenery at a frequency of 0.7 Hz, 1.4_1 first 15 s of measurement in the oscillating scenery at a frequency of 1.4 Hz, 1.4_2 second 15 s of measurement in the oscillating scenery at a frequency of 1.4 Hz, 0.7_before—first 15 s of measurement in the oscillating scenery with the change in oscillation frequency from 0.7 Hz to 1.4 Hz, 1.4_after—second 15 s of measurement in the oscillating scenery with the change in oscillation frequency from 0.7 Hz to 1.4 Hz, 1.4_before—first 15 s of measurement in the oscillating scenery with the change in oscillation frequency from 1.4 Hz to 0.7 Hz). (**A**) Median of mean COP velocity in the AP direction and (**B**) Range of COP movement in the AP direction. statistically significant differences were found only in experiments where the frequency of the oscillating scenery changed from 1.4 Hz to 0.7 Hz. Figure 5: **(A–D)** TCI Values. **(A)** TCI for the whole measurement period; **(B)** TCI for the 0–0.2 s period; **(C)** TCI for the 0.2–0.5 s period; **(D)** TCI for the 0.5–1 s period. Figure 5B shows the TCI values obtained for the period of 0-0.2 s. The introduction of disturbances into VR decreased the values of the median TCI in this period. A decrease in the median values was noticeable in the case of higher frequency oscillations in comparison to those with a lower frequency. Based on the diagram presenting the TCI values for the period of 0.2-0.5 s (Figure 5C), one can observe that higher values of the median occurred in the measurements using the scenery oscillating at a frequency of 1.4 Hz. The median values in the case of disturbances at a frequency of 0.7 Hz were similar to the OE and CE values. For the period of 0.5-1 s, the highest values were observed in the VR tests with disturbances at a frequency of 0.7 Hz (Figure 5D), whereas the lowest values were observed at a 1.4 Hz frequency. When comparing OE and CE measurements, no statistically significant differences were observed. By contrast, statistically significant differences were observed between the results obtained in the real-life environment and those in the virtual environment for all  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & & \multicolumn{1}{c}{**TCI**} & \multicolumn{1}{c}{**TCI**} & \multicolumn{1}{c}{**TCI**} \\  & & **TCI** & **(0-0.2s)** & **(0.2–0.5s)** & **(0.5–1s)** \\ \hline OE & CE & 1.00 & 1.  
time periods in most cases. From 0-0.2 s, statistically significant differences were observed between measurements 0.7_1 and 0.7_2, 1.4_1 and 1.4_before, and 0.7_before and 1.4_after.