Suppose (for example) that I knew with 100% certainty that the global demand for home robotics would grow tenfold in the next decade.

If you have 100% confidence in something, you then logically should go for maximum leverage, regardless of the risk, and so stock up on derivatives, like options and futures, rather than buy and hold stocks or indices.

But of course people are generally poorly calibrated, so someone who thinks they are 100% right will probably be wrong half the time.