Sklansky, tortoise, hare.....why?

[Johnny 99]

Sklansky writes: [ QUOTE ]
your excess winning or losing swings do not increase proportionately to the number of hours you play. Rather, they increase proportionally to the square root of the number of hours played.


[/ QUOTE ]

I'm curious how this conclusion is reached (and I have no cause to doubt its validity). Sure one's win rate will start to chip away at their bad luck until they are no longer losing, but how could we know that it increases proportionally to the square root of the number of hours played?

Is it the result of empirical studies? Is it derived from self evident principles? Does it just "sound about right"?

I have similar questions as to how statistical concepts are derived and perhaps the answer to this will help.

Thanks,