It's impossible to predict the exact outcome, but some outcomes are far more likely than others
Absolutely, but statistical trends and predictions never work when you try and infer the particular outcome of an individual case. For example, if we are talking mixed race marriages, there's a whole lot of stats that you'll find that talk about the general trend of the degree of success in marriages between 2 particular races (and filtered down further, by age etc), but none of that would be useful if you try and guess how a particular couple is going to do or how successful their marriage will be.
The differences in race, culture etc between Bobs and his fiancee could really test them at times, but I'm sure at other times, those same differences could lead to greater attraction and so forth. No one knows how long a marriage will last, including the couple themselves - you just hope for the best and do what is needed, I guess.
