I want to analyze the probability of error at the output of a cascade of latches. I'm a bit confused about the equation (17) in the "comparator metastability analysis" article in this forum. It says that if Pe1 and Pe2 are the metastabilility probability errors of two latches in cascade, then the total prob of error is :

Pe = Pe1*Pe1;

But what I think, it should be Pe1 +Pe2;

Is it correct ?