In a two-child family, if one child is a boy, what is the probability that the other child is a girl? If the first child is a boy, what is the probability that the second is a girl?
If we assume that birth gender probability is equiprobable and independent within a family:
It should be noted that the male:female birth ratio is not really
Also within a family there is often a bias towards a particular gender (however I haven't seen any recent studies on the actual degree of this bias).
Sequence should not have any effect on the gender probability (except for the intra-family bias mentioned above).