I have formed more or less a consistent way to look at an investment, decision or undertaking(learnt from expert poker players)
For me, each investment, decision or undertaking(i call a bet) always could be looked at from the probability view point.
Each bet has a probability of being right(Pr) and a probability of being wrong(Pw). When a bet is taken and the investor is right, he earns the gain for being right. Conversely, when the investor is wrong, he incurs a loss for being wrong.
I make a decision to bet or not based on the possibility to determine how big the difference is*
[(Pr x gain) - (Pw x loss) ] > threshold
With the difference being the larger the better for the bet.
The difficulty is that it is always difficult to work out precise probability in a bet(unlike probability exam questions). *I always believe the more hard work one puts into research, the more accurate probability would be.
You could use same approach to try to calculate whether you should marry someone, have childrens, pick a school, a type of degree or anything that has a risk factor for that matter.