Michael Mauboussin, head of Global Financial Strategies at Credit Suisse, has written extensively on the role of skill vs. luck in many endeavors ... mostly for business, sports and investing.

He is well worth paying attention to.

This, in particular:

There is actually a very interesting test to determine if there is any skill in an activity, and that is to ask if you can lose on purpose. If you can lose on purpose, then there is some sort of skill. Investing is very interesting because it is difficult to build a portfolio that does a lot better than the benchmark. But it is also actually very hard, given the parameters, to build a portfolio that does a lot worse than the benchmark. What that tells you is that investing is pretty far over to the luck side of the continuum. That is the first important thing.

From that one paragraph, and the logical conclusions that follow (there is a lot more to it than that one paragraph) ... a few important points:

  • There is a continuum of luck to skill
  • Investing (I'd substitute 'trading' in there) has elements of both ... "pretty far over to the luck side of the continuum"
  • Given it's a spectrum, there is skill involved
  • Skill can be improved

More from the article. Bolding is mine:

  • ... how to improve one's skill
  • When you're on the skill side of the continuum, your output and your skill are very closely related to one another
  • When you move over to the luck side, it becomes process-oriented and probabilistic. ... you really have to focus on process

OK, here's the link: The Role of Luck and Skill in Investing

There is plenty more on Mauboussin on the web. And, of course, much more detail in his book, much better than the snippets you'll find around the web.