Vic, I know that my q may not make sense, but all the same are...

Vic, I know that my q may not make sense, but all the same are you able to assist the calculation, please? I can accept the assumption that the std Dev is similar so let's run with that?

'Yes this was what I was asking, and sorry for not articulating in one sentence as you have done. Based on the assumption that the final 400 will yield the same data at the original 600, is it possible from stats to predict the P value for the 600? I understand it would be higher than 0.01 as it would be less powered, but I have no idea as to how to calculate the number.'