Can anyone who has a better understanding on how profitability is calculated explain to beginners like me ? I assume it's not as simple as value of the coin relative to BTC and difficulty of the coin. I'm having trouble understanding how it works..I check the last rounds and it seems pretty obvious that certain coins never yield more than 0.0000xx (4 zeroes) whereas others yield 0.000xxx (3 zeroes) for the same amount of time. (and for my 950 kh). I also understand there's a luck factor involved..however I dont see why we would switch from a coin producing say 0.000xxx in 1 hour to 0.0000xx in the same period of time..can't we keep on rolling on that one ? What changed so that the algorithm decided that the 2nd coin is better?

thanks in advance..im just trying to understand how it works