Mrs. Allen is about to have another baby. She already has three daughters. What is the probability that her fourth child will also be a girl?

The probability her 4th child will be a girl is 0.5

Explanation:

during pregnancy or child birth, the gender of a baby is not affected by the gender of the previous baby in the womb. Rather it is determined by the type of chromosomes supplied by the father of the baby.

If X chromosomes are supplied, a girl will be born because the baby will have xx chromosomes. If Y chromosomes are supplied, the baby will have YY chromosomes which means that he is a boy.

Hence there are equal chances of the baby being a boy or a girl, each time a woman is pregnant. The probability of the baby being a boy or a girl is the same and it 0.5