Quote from Shanb:
I guess alot of it depends on what you are trading. Also ask yourself what does ACD represent and how can it help in my trading? ACD is a lens to view market volatility. Markets tend to have certain characteristics...range expansion, momentum, mean reversion. You are trying to capture that behavior. If you are playing breakouts in CL you would want to use an OR small enough that captured the price discovery period, but big enough that it still kept you out of noise.
I've used ATR for my A and C levels and they work very well. They work very well in commodities and the indices, less so in some illiquid stocks.