I have argued this on a thread before and not quite long, but maybe I am wrong. If you are not betting on sport like football, do not bother to choose either yes or no.
Since I have been betting, I have not thought of this before. Is the referee the reason you bet on yellow or red cards?
It's a clever thought and every referee will have an average yellow/red cards per match statistic which should theoretically be included in the odds that a bookmaker is offering. However it has to be blended with more than just the ref, some teams will play very cleanly with an emphasis on avoiding cards, while others have a reputation for playing very rough. I'd say it's more important to look at the likelihood of particular players getting a card rather than the ref - as they are probably playing more dirty and will be a magnetic for cards. Referees are also probably monitored by the official organisations and will be encouraged to stay within a certain range - so as not to create too many or too few in comparison to other refs.