Im day trading a live account with some success at least pip wise but as each trade goes by i always find myself asking would it have been different on a different time scale, i currently use the 15 min chart then look higher up to 30 mins and 1hr as further confirmation of trend and whatnot, my system can confirm on any time scale, it will look the same each time so what im asking is
For a day trader which is the best time frame to use, which is the most popular so im seeing what the majority are seeing. 
Thanks