Using the International 10-20 electrode placements, if the distance from Fp2 to F4 is 5.5 cm, what is the distance from P4 to O2?

The correct answer is based on the principles of the International 10-20 System of electrode placement, which is designed to achieve standardized and reproducible electrode locations on the scalp. The key to understanding this question lies in recognizing that the distances between specific points on the head in this system often follow a consistent ratio.

In this system, the reference points Fp2 (Frontopolar) to F4 (Frontal) can provide a baseline measurement for calculating distances to other electrode locations. Given that the distance between Fp2 and F4 is known to be 5.5 cm, we can apply that measurement to estimate the distance from P4 (Parietal) to O2 (Occipital).

The distance between P4 and O2 is also based on the same anatomical mapping principles as the other electrode pair. Since the 10-20 system maintains proportional distances, and with the distance from Fp2 to F4 being established, it follows logically that the distance from P4 to O2 will also reflect a similar measurement. In this case, 5.5 cm is consistent with the expected distances between these specific electrode positions.

Thus, the distance from P4 to O2 being 5.5 cm aligns well with