Which EEG electrode site is located half the distance from O1 to T3?

The electrode site that is located half the distance from O1 to T3 is T5. In the International 10-20 System of EEG electrode placement, the positioning of electrodes is based on specific landmarks on the skull.

The O1 electrode is placed over the left occipital area, while T3 is located at the temporal region. The point T5 is positioned along the same horizontal plane as T3 but is moved backward towards the occipital region, making it halfway between O1 and T3 in terms of distances.

Understanding the relationships and measurements between these different electrode sites is essential in EEG recordings, as it impacts the accuracy of interpreting brain activity. T5, therefore, is the correct electrode site for this particular question based on its spatial relationship to O1 and T3.