Now .. the problem is to find where the bottom and whre is the peak price is? .. so that the ratio can be apply.. so to solved this problem most TA's people... they like to overlay various high peak and lows and chose whre the like price will fall to and take necessary action after that move...
For train eye TA there are very good in determine the high and low.. by just looking at the chart..but for me a novice TA ,, trial errror will solved this problem...
With little bit of luck they use Fib ratio to find the low for the buy signal... After series of experimenting my favorite FIB ratio is 50% if this number is reached with confirming internal of rsi or macd or other internal then that signal then one can 78% confident of entering the trade..
eg of bouested chart of which i am monitoring ,, it fall nicely at 50% at 3.77 and go to 4.77 naik nearly 21.4% from bottom .. the PROs are using it so we follow..
Just my IMHO I like Fibonacci trader software as my study