There are lots of disadvantage of technical analysis:
Interference: Technical analysis is very one-sided. Quick changes in the plan may have an unfavourable impact on the trading results. What may seem on the chart to signal to enter the market, in fact, will be only a noise, that can be tracked only on large frames.
Controversial conclusions: Technical indicators may show the signals. Different traders may understand exactly the opposite. Interestingly, both traders will find lawful confirmation of his conclusions, and even quite logical.
The time lag: Signals can be delayed; the trader may also be late indecision. By the way, regarding the lag, the Dow Theory is often criticized.
If you want to learn technical and fundamental analysis you can join any institute like NIFM, NSE India, ICFM, Share market Shiksha.
(Source: https://www.quora.com/What-are-the-disadvantages-of-techinical-analysis)
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