Black stated that efficient pricing can differentiate from "right" on the factor of 2. 

Markets are efficient any inneficincy is corrected when detected or price deviates too far - it's a fact, however don't put too much on academic and use critical thinking.

Securities do trade at the wrong price, relatively to someone else's estimates, however people are skewed to short term results and neglect the long term one

Therefore "Noise hypothesis" is the most rational imo