There are a few people out there, like Bulkowski, that have attempted to put a probability behind each chart formation. The probability that he assigns usually goes something like 55% or 60%...basically, a little better then coin flip odds.
Many folks on the internet will throw up a chart without acknowledging the probability is little more then a coin flip and that is only if you are interepting it right. They make it seem like geometry is a 100% fool proof thing.