[Teddiursa of the Sky]

There is a 78% chance that Ash and friends are right-handed and a 22% chance they are left-handed. Since the percentage of the amount of right and left-handed people, for some odd reason, always stays the same no matter how large the human population of Earth may be, (genes are a weird thing aren't they?) I would say he and his friends are right-handed since there is a larger chance that they are and until proven otherwise, I will think that way.

It seems that television characters are ambidextrous, for the same reason they always wear the same clothes. So they do not confuse the small children watching, plus who pays attention to such detail. Asking a question like that is like asking where and when Ash and friends take a crap.