If the measured distance from the nasion to the inion is 36 cm, what is the distance from Cz to Pz?

To determine the distance from Cz to Pz based on the measured distance from the nasion to the inion, it’s important to understand the relationships and proportions defined by the international 10-20 system used in EEG electrode placement.

The nasion to inion distance is often used as a reference for determining various other distances on the head. According to the 10-20 system, the distance from Cz (the central point) to Pz (the parietal point) is generally about 20% of the total nasion to inion distance.

In this case, if the distance from the nasion to the inion is 36 cm, then calculating 20% of that distance gives us:

[

0.20 \times 36 \text{ cm} = 7.2 \text{ cm}

]

This calculation precisely matches with the choice indicating that the distance from Cz to Pz is 7.2 cm. Therefore, the answer correctly reflects the established proportional relationship within the framework of EEG electrode placements, illustrating how specific distances can be inferred from a key measurement like the nasion to inion distance.