Assuming boys and girls are equally likely, find the probability of a couple having a baby boy when their fourth child is born, given that the first three were all boys.
When each child is born, there are two equally likely possibilities: boy or girl. Since the gender of each child is independent of each other, the probability of having a boy for each birth is 1/2.
Given that the first three children were all boys, the couple already has three boys. When the fourth child is born, there are still two equally likely possibilities: boy or girl.
Since the first three children were boys, these births do not affect the gender of the fourth child. Therefore, the probability of having a baby boy when their fourth child is born is still 1/2.