[Eeglablist] Question about adding back the reference channel

[April Luo]

Hello EEGlab list,

I have 32 channels and I'm using the pop_reref function to P9, so after the
pop_reref function, the total channel number is 31. After going through
ICA, I want to add P9 back, I saw from this video (
https://urldefense.com/v3/__https://www.youtube.com/watch?v=hByLyGYecjI__;!!Mih3wA!EMcXas_4mWxY8pat-CJTKsqR5YiEbMtCiLd4YEBXSjl_YFuYLnCVGB4Dz4MtFouxhQy5KnFSI3ws2832XMUoODY$  ) that I can calculate the
reference electrode by using P9 = -SE/33 (SE: summed electrode activity,
and 33: total channels + 1), but I'm not sure what would be SE in this
case? And is my understanding correct?


Thank you,
Best,
April Luo