Double top vs. Cup and Handle

Tweet

I've been practicing technical analysis. I've come across these two chart patterns and they seem to be really similar with the the end result differing. In the double top we can expect a fall after the last top whereas after the second top in the cup and handle patter there is usually a small drop followed by a spike. Obviously in the former pattern a trader would want to sell as close to the second top as possible and in the later he or she would want to buy. What I'd like to know is how do we know if a pattern will develop into a double top or cup and handle.