Making a 10% move with 1 stock makes the same pnl as making a 5% move with 2 stocks. Thus it makes very much sense to find out when presumed risk allows me to bet more. Then, why do people never talk about variations in position size? Why are there so many concepts about signals/exits and so few about variance of position size? Do daytrader no care? Or are they not aware? Do you vary your position size in response to the market?