How reliable is technical analysis?

Part of the decline of technical analysis can be attributed to the random walk hypothesis, a component of the Chicago theory developed in the early 1960s, primarily by Professor Eugene Fama. The random walk hypothesis says a stock’s past price movements are of absolutely no help in predicting future movements. In other words, it’s a random process, like tossing a coin. We all know that even if a coin has come up heads ten times in a row, the probability of heads on the next throw is still fifty-fifty. Like-wise, the hypothesis says, the fact that a stock’s price has risen for the last ten days tells you nothing about what it will do tomorrow.

How reliable is technical analysis?